1 Atomic Structure

SCIENCE VISUAL RESOURCES CHEMISTRY

An Illustrated Guide to Science

The Diagram Group Chemistry: An Illustrated Guide to Science

Author: Derek McMonagle BSc PhD CSci CChem FRSC

Editors: Eleanora von Dehsen, Jamie Stokes, Judith Bazler

Design: Anthony Atherton, Richard Hummerstone, Lee Lawrence, Phil Richardson

Illustration: Peter Wilkinson

Picture research: Neil McKenna

Indexer: Martin Hargreaves

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ISBN 0-8160-6163-7

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CP Diagram 10 9 8 7 6 5 4 3 2 1

This book is printed on acid-free paper. Introduction

Chemistry is one of eight volumes of the Science Visual Resources set. It contains eight sections, a comprehensive glossary, a Web site guide, and an index.

Chemistry is a learning tool for students and teachers. Full-color diagrams, graphs, charts, and maps on every page illustrate the essential elements of the subject, while parallel text provides key definitions and step-by-step explanations.

Atomic Structure provides an overview of the very basic structure of physical matter. It looks at the origins of the elements and explains the nature of atoms and molecules.

Elements and Compounds examines the characteristics of the elements and their compounds in detail. Tables give the boiling points, ionization energies, melting points, atomic volumes, atomic numbers, and atomic masses key elements. Plates also describe crystal structures and covalent bonding.

Changes in Matter is an overview of basic chemical processes and methods. It looks at mixtures and solutions, solubility, chromatography, and the pH scale.

Patterns—Non-Metals and Patterns—Metals focus on the properties of these two distinct groups of elements. These sections also include descriptions of the industrial processes used when isolating important elements of both types.

Chemical Reactions looks at the essential factors that influence reactions. It includes information on proton transfer, electrolysis, redox reactions, catalysts, and the effects of concentration and temperature.

Chemistry of Carbon details the chemical reactions involving carbon that are vital to modern industry—from the distillation of crude oil to the synthesis of polymers and the manufacture of soaps and detergents. This section also includes an overview of the chemistry of life.

Radioactivity is concerned with ionizing radiation, nuclear fusion, nuclear fission, and radioactive decay, as well as the properties of radiation. Tables describe all known isotopes, both radioactive and non-radioactive. Contents

1 ATOMIC STRUCTURE

8 Formation of stars 18 Measuring the charge on the 9 Fate of stars electron 10 The solar system 19 Size and motion of 11 Planet composition molecules 12 Planetary density, size, and 20 Determination of Avogadro’s atmosphere constant 13 Atomic structure 21 The mole 14 Geiger and Marsden’s 22 Atomic emission spectrum: apparatus hydrogen 15 Investigating the electron 1 23 Energy levels: hydrogen 16 Investigating the electron 2 atom 17 Cathode ray oscilloscope 24 Luminescence

2 ELEMENTS AND COMPOUNDS

25 Organizing the elements 36 Periodic table with masses 26 The periodic table and numbers 27 First ionization energies of 37 Calculating the molecular the elements mass of compounds 28 Variation of first ionization 38 Structure of some ionic energy crystals 29 Melting points of the 39 Crystal structure of metals: elements °C lattice structure 30 Variation of melting 40 Crystal structure of metals: points efficient packing 31 Boiling points of the 41 Chemical combination: ionic elements °C bonding 32 Variation of boiling points 42 Chemical combination: ionic 33 Atomic volumes of the radicals elements 43 Chemical combination: 34 Variation of atomic covalent bonding volumes 44 Chemical combination: 35 Atomic mass coordinate bonding

3 CHANGES IN MATTER

45 Mixtures and solutions 50 Gas-liquid chromatography 46 Colloids and mass spectrometry 47 Simple and fractional 51 The pH scale distillation 52 Indicators 48 Separating solutions 53 Titration of strong acids 49 Paper chromatography 54 Titration of weak acids 55 pH and soil 60 Ionic solutions 56 The water cycle 61 Solubility 57 Treatment of water and 62 Solubility curves sewage 63 Solubility of copper(II) 58 The water molecule sulfate 59 Water as a solvent of ionic salts

4 PATTERNS—NON-METALS

64 Hydrogen: preparation 82 Oxygen and sulfur: 65 Hydrogen: comparative allotropes density 83 Oxygen and sulfur: 66 Hydrogen: reaction with compound formation other gases 84 The oxides of sulfur 67 Hydrogen: anomalies in 85 Industrial preparation of ammonia and water sulfuric acid (the contact 68 Basic reactions of hydrogen process): theory 69 The gases in air 86 Industrial preparation of 70 Nitrogen sulfuric acid (the contact 71 Other methods of process): schematic preparing nitrogen 87 Affinity of concentrated 72 The nitrogen cycle sulfuric acid for water 73 Preparation and properties 88 Oxygen and sulfur: of ammonia oxidation and reduction 74 Industrial preparation of 89 Basic reactions of oxygen ammonia (the Haber 90 Basic reactions of sulfur process): theory 91 The halogens: group 7 75 Industrial preparation of 92 Laboratory preparation of ammonia (the Haber the halogens process): schematic 93 Compounds of chlorine 76 Industrial preparation of 94 Hydrogen chloride in nitric acid solution 77 Nitrogen: reactions in 95 Acid/base chemistry of the ammonia and nitric acid halogens 78 Basic reactions of nitrogen 96 Redox reactions of the 79 Nitrate fertilizers halogens 80 Oxygen and sulfur 97 Reactivity of the halogens 81 Extraction of sulfur—the Frasch process

5 PATTERNS—METALS

98 World distribution of metals 101 The group 1 metals: 99 Main ores of metals sodium 100 The group 1 metals 102 The group 2 metals 103 The group 2 metals: general 111 Reactions of copper reactions 112 Reaction summary: 104 The transition metals: aluminum, iron, and copper electron structure 113 The extraction of metals 105 The transition metals: from their ores ionization energies and 114 Reactivity summary: physical properties metals 106 Aluminum 115 Tests on metals: flame test 107 Iron: smelting 116 Tests on metals: metal 108 The manufacture of steel hydroxides 109 Rusting 117 Tests on metals: metal ions 110 Copper smelting and 118 Uses of metals converting

6 CHEMICAL REACTIONS

119 Reactivity of metals 1 134 Rates of reaction: 120 Reactivity of metals 2 concentration over time 121 Electrolysis 135 Rate of reaction vs. 122 Electrolysis: electrode concentration activity and concentration 136 Variation of reaction rate 123 Acids: reactions 137 Rates of reaction: effect of 124 Preparation of acids temperature 1 125 Bases: reactions 138 Rates of reaction: effect of 126 Bases: forming pure salts temperature 2 127 Proton transfer: 139 Exothermic and neutralization of alkalis endothermic reactions 128 Proton transfer: 140 Average bond dissociation neutralization of bases energies 129 Proton transfer: metallic 141 Catalysts: characteristics carbonates 142 Catalysts: transition 130 Proton transfer: metals neutralization of acids 143 Oxidation and reduction 131 Collision theory 144 Redox reactions 1 132 Rates of reaction: surface 145 Redox reactions 2 area and mixing 146 Demonstrating redox 133 Rates of reaction: reactions temperature and 147 Assigning oxidation state concentration

7 CHEMISTRY OF CARBON

148 The allotropes of carbon: 151 Laboratory preparation of diamond and graphite carbon oxides 149 The allotropes of carbon: 152 The fractional distillation of fullerenes crude oil 150 The carbon cycle 153 Other refining processes 154 Carbon chains 165 Esters 155 Naming hydrocarbons 166 Soaps and detergents 156 Table of the first six alkanes 167 Organic compounds: states 157 Table of the first five 168 Functional groups and alkenes properties 158 Ethene 169 Reaction summary: alkanes 159 Polymers and alkenes 160 Polymers: formation 170 Reaction summary: alcohols 161 Polymers: table of and acids properties and structure 171 Optical isomerism 162 Functional groups and 172 Amino acids and proteins homologous series 173 Monosaccharides 163 Alcohols 174 Disaccharides and 164 Carboxylic acids polysaccharides

8 RADIOACTIVITY

175 Ionizing radiation 189 The neptunium series 176 Radiation detectors 190 Radioactivity of decay 177 Properties of radiations: sequences penetration and range 191 Table of naturally occurring 178 Properties of radiations: in isotopes 1 fields 192 Table of naturally occurring 179 Stable and unstable isotopes 2 isotopes 193 Table of naturally occurring 180 Half-life isotopes 3 181 Measuring half-life 194 Table of naturally occurring 182 Radioactive isotopes isotopes 4 183 Nuclear fusion 195 Table of naturally occurring 184 Nuclear fission isotopes 5 185 Nuclear reactor 196 Table of naturally occurring 186 The uranium series isotopes 6 187 The actinium series 197 Table of naturally occurring 188 The thorium series isotopes 7

APPENDIXES

198 Key words 205 Internet resources 207 Index

ATOMIC STRUCTURE Formation of stars

Key words Big Bang supernova black hole white dwarf brown dwarf neutron star protostar Big Bang Beginnings ● According to the Big Bang theory, the universe resulted from a massive explosion that created matter, space, and time. ● During the first thee minutes following the Big Bang, hydrogen and helium were formed as the universe began to Hydrogen and helium cool. Initial formation ● Stars were formed when gravity caused Gravity clouds of interstellar gas and dust to contract. These clouds became denser and hotter, with their centers boiling Collected mass of liquid at about a million kelvins. hydrogen and helium ● These heaps became round, glowing blobs called protostars. ● Under the pressure of gravity, 1 × Sun 10 × Sun 10(+) contraction continued, and a protostar Too little × Sun gradually became a genuine star. (Brown dwarf) ● A star exists when all solid particles have evaporated and when light atoms such as hydrogen have begun building Nuclear reaction heavier atoms through nuclear (hydrogen → helium) reactions. ● Some cloud fragments do not have the mass to ignite nuclear reactions. These become brown dwarfs. ● The further evolution of stars depends Nuclear reaction Nuclear reaction on their size (See page 9). (hydrogen → carbon) (helium → carbon → iron) ● Stars the size of our Sun will eventually shed large amounts of matter and contract into a very dense remnant—a white dwarf, composed of carbon and oxygen atoms. White dwarf Black ● More massive stars collapse quickly (carbon) hole shedding much of their mass in dramatic explosions called supernovae . After the explosion, the Supernova remaining material contracts into an explosion extremely dense neutron star. ● The most massive stars eventually mation Ltd.

or collapse from their own gravity to black holes, whose density is infinite.

Visual Inf Many heavy elements + neutron star © Diagram 9

Fate of stars ATOMIC STRUCTURE

Key words 1 The fate of a star the size of our sun black hole supernova a b c d e f fusion white dwarf neutron star red giant

Fate of stars ● During most of a star’s life, the outward pressure from nuclear fusion balances the pull of gravity, but as nuclear fuel is exhausted, gravity compresses the star inward and the Time core collapses. How and how far it collapses depends on the size of the star.

2 Fate of a larger star 1 The fate of a star the size of our sun ● A star the size of our Sun burns hydrogen into helium until the hydrogen is exhausted and the core begins to collapse. This results in nuclear fusion reactions in a shell around the core. The outer shell heats up and expands to produce a red giant. ● Ultimately, as its nuclear reactions subside, a red giant cools and contracts. Its core becomes a very g h small, dense hot remnant, a white Time dwarf. i j k 2 Fate of a larger star ● Stars with an initial mass 10 times that 3 Fate of a massive star of our Sun go further in the nuclear fusion process until the core is mostly carbon. The fusion of carbon into larger nuclei releases a massive amount of energy. The result is a huge explosion in which the outer layers of the star are blasted out into space. This is called a supernova. ● After the explosion, the remaining material contracts, and the core Time collapses into an extraordinary dense l m n object composed only of neutrons— a neutron star. a hydrogen is converted to helium i The collapsed star suddenly expands rapidly, b planetary system evolves creating a supernova explosion 3 Fate of a massive star c hydrogen runs out and helium is converted j creates many different elements ● Stars with an initial mass of 30 times

to carbon k the core of the dead star becomes a neutron mation Ltd. d star cools to form a red giant star our Sun undergo a different fate or e carbon l hydrogen converted to many different altogether. The gravitational field of f star evolves to form a white dwarf elements g hydrogen is converted to helium and carbon, m hydrogen runs out, and the star collapses to such stars is so powerful that material Visual Inf and eventually iron form a black hole cannot escape from them. As nuclear h hydrogen runs out, and star undergoes n black hole reactions subside, all matter is pulled

gravitational collapse © Diagram into the core, forming a black hole. 10

ATOMIC STRUCTURE The solar system

Key words 1 Birth of the solar system 3 Inner planets ammonia Mercury fission helium hydrogen methane

1 Birth of the solar system ● The solar system is thought to have formed about 4.6 billion years ago as a f g result of nuclear fission in the Sun. ● A nebula (cloud) of gases and dust Mars c that resulted from the explosion. flattened into a disk with a high b concentration of matter at the center. 2 Formation of the inner a and outer planets ● Near the Sun, where the temperature was high, volatile substances could not h i condense, so the inner planets (Mercury, Venus, Earth, and Mars) are f light shell dominated by rock and metal. They g dense core h light shell are smaller and more dense than those i dense core farther from the Sun. ● In the colder, outer areas of the disk, substances like ammonia and 4 Outer planets methane condensed, while hydrogen Uranus and and helium remained gaseous. In this Neptune region, the planets formed (Jupiter, k Saturn, Uranus, and Neptune) were gas giants. j a hydrogen and helium b heavier elements 3 Inner planets c lighter elements ● Inner planets consist of a light shell l surrounding a dense core of metallic elements. ● Mercury, the planet closest to the Sun, j diameter = 2 or 3 that of the Earth k solid water, methane, and ammonia has a proportionately larger core than l liquid water, methane, and ammonia Mars, the inner planet farthest from the Sun. 2 Formation of the inner and outer planets d Jupiter and Saturn 4 Outer planets m e ● The outer planets have low densities and are composed primarily of hydrogen and helium. ● The outer planets are huge in comparison to the inner planets. ● Jupiter and Saturn, the largest of the o gas giants, contain the greatest mation Ltd. n

or percentages of hydrogen and helium; the smaller Uranus and Neptune m liquid hydrogen and helium

Visual Inf contain larger fractions of water, n small rocky center ammonia, and methane. o radii: d denser inner planets Jupiter = 11 × radius of Earth e less dense outer planets Saturn = 9 × radius of Earth © Diagram 11

Planet composition ATOMIC STRUCTURE

Key words 1 Basic composition of the planets atmosphere oxide a b c d carbonate sulfate crust mantle nitrate

Iron/nickel core shell of silicon and other elements 1 Basic composition of the planets ● The inner planets—Mercury, Venus, e f Earth, and Mars—consist of an iron–nickel core surrounded by a shell of silicon and other elements. ● The outer planets—Jupiter, Saturn, Uranus, and Neptune—consist largely of solid or liquid methane, ammonia, liquid hydrogen, and helium. ● Pluto is not included in this comparison because it is atypical of the other outer planets, and its origins are uncertain. 2 Composition of Earth ● Earth consists of a dense, solid inner core and a liquid outer core of nickel Liquid hydrogen and helium and iron. The core is surrounded by the mantle (a zone of dense, hot rock), and finally by the crust, which is g h the surface of Earth. ● Since most of the materials of Earth are inaccessible (the deepest drilled holes only penetrate a small distance into the crust), we can only estimate the composition of Earth by looking at Solid/liquid water, methane, and ammonia the composition of the materials from which Earth formed. Meteorites a Mercury c Earth e Jupiter g Uranus provide this information. b Venus d Mars f Saturn h Neptune ● Oxygen is the most common element on Earth, and about one fifth of Earth’s atmosphere is gaseous oxygen. 2 Composition of Earth ● Oxygen is also present in many

Composition % compounds, including water (H2O), i of Earth m carbon dioxide (CO2), and silica oxygen 46 (SiO2), and metal salts such as oxides, j silicon 28 aluminum 8 carbonates, nitrates, and sulfates. k iron 5 n calcium 4 sodium 3 l potassium 3 magnesium 2 mation Ltd. or

i crust l inner core (solid – nickel and iron) Visual Inf j mantle (oxygen, silicon, aluminum, iron) m crust, mantle, and oceans = 2/3 of mass) k outer core (liquid – nickel and iron) n core = 1/3 of mass © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● of theinnerplanets 2 ● ● planets 1 photosynthesis chlorophyll carbon dioxide atmosphere Key words of greenplants. par composition oftheatmosphere.Of came drasticchangestothe photosynthesis carbohydrates. Theprocessiscalled trap energyfromsunlightandmake life tostar allowed conditionsonEarth particular However,the planetsformed. the planets haveremainedunchanged. it, andtheatmospheresonthese were notsuitableforlifeasweknow adjacent toEarth—Venus and Mars— Conditions onthetwoplanets plants. Thus, animalscouldevolvealongside the energytheyneededtosurvive. providedanimalswith which inturn, theSun’senergyintofood, turning The greenplantsprovidedameansof present levelofabout0.04percent. atmosphere felluntilitreachedthe of proportion Ear As chlorophyll Green plantscontainapigmentcalled Earth’s inner planets. large buthavealowerdensitythanthe Uranus, andNeptune—arerelatively The outerplanets—Jupiter, Saturn, outer planets. but haveahigherdensitythanthe andMars—arerelativelysmall Earth, The innerplanets—Mercury, Venus, similar tothatofV Densities andradiiofthe Atmospheric composition ticular importance istheevolution ticular importance ATOMIC STRUCTURE th becamegreener, the atmosphere t and flourish.With this . Plants usethispigmentto carbon dioxide . 12 enus andMarswhen was probably in the c b a 1 Density (relative to water) and atmosphere Planetary density,size, 2 Earth Venus Mercury Densities andradiioftheplanets 1 2 3 4 6 5 7 a b a b Atmospheric compositionoftheinnerplanets Others Oxygen Nitrogen Carbon dioxide c d d c e Venus e Distance from Sun(inmillionsof miles) ,0 3,000 1,000 f f e d Saturn Jupiter Mars f Density Radius Earth g g 2,000 h g Mars Neptune Uranus h h 50,000 60,000 70,000 0 10,000 20,000 30,000 40,000

Radius (in km) 13

Atomic structure ATOMIC STRUCTURE

1 Principle subatomic particles Key words atom neutron Particle Relative atomic mass Relative charge atomic number nucleus 1 Electron 1836 –1 electron proton Neutron 1 0 isotope subatomic mass number particle Proton 1 1 1 Principle subatomic 2 The atom particles ● An atom is the smallest particle of an + proton element. It is made up of even smaller nucleus neutron subatomic particles: negatively charged electrons, positively charged protons, and neutrons, which have no electron charge.

+ + + 2 The atom + ++ + + ● An atom consists of a nucleus of + + + protons and neutrons surrounded by a number of electrons. ● Most of the mass of an atom is contained in its nucleus. 7Li ● The number of protons in the nucleus 3 is always equal to the number of electrons around the nucleus. Atoms have no overall charge. 3 Representing an element 3 Representing ● Elements can be represented using an element their mass number, atomic number, and atomic symbol: mass number + atomic number Symbol + + ● The atomic number of an atom is the number of protons in its nucleus. ● The mass number is the total number of protons and neutrons in its nucleus. Thus, an atom of one form of lithium (Li), which contains three protons and four neutrons, can be represented as: 7 3Li 4 Isotopes ● All atoms of the same element have 4 Isotopes the same atomic number; however, they may not have the same mass number because the number of neutrons may not always be the same. Atoms of an element that have different mass numbers are called + + + isotopes. The diagram at left illustrates mation Ltd.

isotopes of hydrogen. or Visual Inf

Hydrogen 1 Hydrogen 2 Hydrogen 3 © Diagram 14

ATOMIC STRUCTURE Geiger and Marsden’s Key words apparatus alpha particle atom atomic mass b c d

Developing the atomic model ● At end of the 19th century, scientists thought that the atom was a positively charged blob with negatively charged electrons scattered throughout it. At the suggestion of British physicist Ernest Rutherford, Johannes Geiger and Earnest Marsden conducted an experiment that changed this view of the atomic model. a ● Scientists had recently discovered that some elements were radioactive—they emitted particles from their nuclei as a result of nuclear instability. One type of particle, alpha radiation, is positively charged. Geiger and Marsden investigated how alpha particles scattered by bombarding them against thin sheets of gold, a metal with a high atomic mass. ● They used a tube of radon, a radioactive element, in a metal block (a) as the source of a narrow beam of alpha particles and placed a sheet of gold foil in the center of their apparatus (b). After they bombarded the sheet, they detected the pattern of alpha particle scattering by using a fluorescent screen (c) placed at the focal length of a microscope (d). ● If the existing model had been correct, all of the particles would have been found within a fraction of a degree of the beam. But Geiger and Marsden found that alpha particles were scattered at angles as large as 140°. ● From this experiment, Rutherford deduced that the positively charged alpha particles had come into the repulsive field of a highly concentrated positive charge at the center of the atom. He, therefore, concluded that an mation Ltd. or atom has a small dense nucleus in a source of alpha particles which all of the positive charge and (radon tube) b gold foil

Visual Inf most of the mass is concentrated. c screen Negatively charged electrons surround d microscope the nucleus—similar to the way the

Investigating the ATOMIC STRUCTURE electron 1 Key words anode electron cathode fluorescence 1 Maltese-Cross tube cathode rays a f Investigating the electron + + ● During the last half of the nineteenth century, scientists observed that when – an electric current passes through a glass tube containing a small amount of air, the air glowed. As air was removed, a patch of fluorescence – + appeared on the tube, which they called cathode rays. Scientists then began investigated these streams of electrons traveling at high speed. 1 Maltese cross tube ● In the 1880s, William Crookes experimented on cathode rays using a b c d h e g Maltese cross tube. ● The stream of electrons emitted by the a E.h.t. supply e Maltese-Cross (connected to anode) hot cathode is accelerated toward the b low voltage g shadow anode. Some are absorbed, but the c heated filament and cathode h invisible cathode rays majority passes through and travels d anode f fluorescent screen along the tube. Those electrons that hit the Maltese cross are absorbed. 2 The Perrin tube Those electrons that miss the cross strike the screen, causing it to i q p fluoresce with a green light. ● The result of this experiment is that a + shadow of the cross is cast on the –– – screen. This provides evidence that cathode rays travel in straight lines.

– 2 The Perrin tube – ● In 1895 Jean Perrin devised an experiment to demonstrate that + – – – – cathode rays convey negative charge. + ● He constructed a cathode ray tube in – which the cathode rays were accelerated through the anode, in the form of a cylinder open at both ends, into an insulated metal cylinder called a Faraday cylinder. ● This cylinder has a small opening at one end. Cathode rays enter the cylinder and build up charge, which is j k l m n o indicated by the electroscope. Perrin found that the electroscope had mation Ltd. i E.h.t. supply n vacuum become negatively charged. or j 6 V supply o gold-leaf electroscope ● Perrin’s experiments helped to k cathode p electrons are collected l anode q insulated metal cylinder prepare the way for English physicist Visual Inf m track of electron beam in magnetic field J. J. Thompson’s work on electrons a few years later. © Diagram 16

ATOMIC STRUCTURE Investigating the Key words electron 2 anode photoelectric cathode effect cathode rays radiation 1 J.J. Thomson’s cathode ray tube electron

a e f g h 1 J.J. Thomson’s cathode ray tube –+ ● In 1897 J.J. Thomson devised an experiment with cathode rays that resulted in the discovery of the electron. ● Up to this time, it was thought that the hydrogen atom was the smallest particle in existence. Thomson demonstrated that electrons (which he called corpuscles) comprising cathode rays were nearly 2,000 times smaller in mass than the then lightest-known b c d j i particle, the hydrogen ion. ● When a high voltage is placed across a pair of plates, they become charged a high voltage f direction of travel of the cathode rays b cathode g flourescent screen relative to each other. The positively c gas discharge provides free electrons h light charged plate is the anode, and the d anode with slit i evacuated tube negatively charged plate the cathode. e y-deflecting plate j x-deflecting plate ● Electrons pass from the surface of the cathode and accelerate toward the oppositely charged anode. The anode 2 Evidence of the photoelectric effect absorbs many electrons, but if the anode has slits, some electrons will pass through. k l m ● The electrons travel into an evacuated tube, where they move in a straight line until striking a fluorescent screen. – – This screen is coated with a chemical – + that glows when electrons strike it. – – + –– – + – + + 2 Evidence of the photoelectric effect ● The photoelectric effect is the emission of electrons from metals upon the absorption of electromagnetic radiation. – n – – + + ● Scientists observed the effect in the – – + + nineteenth century, but they could not – + – explain it until the development of o – – quantum physics. ● To observe the effect, a clean zinc plate is placed in a negatively charged Negatively charged The leaf falls as If positively charged electroscope with electrons are ejected the electroscope electroscope. The gold leaf and brass zinc plate attached from the zinc plate remains charged mation Ltd.

or plate carry the same negative charge and repel each other. ● k mercury vapor lamp n gold leaf Visual Inf When ultraviolet radiation strikes the l ultraviolet light o zinc plate zinc plate, electrons are emitted. The m brass plate negative charge on the electroscope is

Cathode ray oscilloscope ATOMIC STRUCTURE

Key words 1 The cathode ray oscilloscope anode a b c d e f cathode cathode rays

1 Cathode ray oscilloscope ● The cathode ray oscilloscope (CRO) is one of the most important scientific instruments ever to be developed. It is often used as a graph plotter to display a waveform showing how potential difference changes with time. The CRO has three essential parts: the electron gun, the deflecting system, and the fluorescent gun. ● The electron gun consists of a heater l k j i h g and cathode, a grid, and several anodes.Together these provide a stream of cathode rays. The grid is at a heater g phosphor coating negative potential with respect to the b y-deflection plates h electron beam cathode and controls the number of c y-input terminal i common-input terminal d x-input terminal j accelerating and focusing anodes electrons passing through its central e x-deflection plates k grid hole. It is the brightness control. f light l cathode ● The deflecting system consists of a pair of deflecting plates across which potential differences can be applied. 2 Electron gun The Y-plates are horizontal but deflect the beam vertically. The X-plates are m n o p vertical and deflect the bean horizontally. ● A bright spot appears on the + fluorescent screen where the beam hits it. – – – 2 Electron gun ● When a current passes through the + heater, electrons are emitted from the surface of the cathode and attracted towards an oppositely charged anode. – + Some will be absorbed by the anode, while others pass through and are accelerated, forming a stream of high- w v u t s r q speed electrons. m low voltage t cathode n heater u evacuated tube o cathode v electron beam p cyclindrical anode w high voltage q high speed electrons mation Ltd.

r accelerated electrons or s anode Visual Inf © Diagram 18

ATOMIC STRUCTURE Measuring the charge on Key words the electron electron radiation Millikan’s apparatus a

Measuring the charge on the electron ● In the early part of the 20th century, b American physicist Robert Millikan constructed an experiment to accurately determine the electric charge carried by a single electron. ● Millikan’s apparatus consisted of two horizontal plates about 20 cm in diameter and 1.5 cm apart, with a small hole in the center of the upper plate. c ● At the beginning of the experiment, an atomizer sprayed a fine mist of oil on to the upper plate. ● As a result of gravity, a droplet would pass through the hole in the plate into a chamber that was ionized by radiation. Electrons from the air attached themselves to the droplet, causing it to acquire a negative charge. A light source illuminated the droplet, d making it appear as a pinpoint of light. Millikan then measured its downward e velocity by timing its fall through a known distance. ● Millikan measured hundreds of f droplets and found that the charge on them was always a simple multiple of a basic unit, 1.6 x 10-19 coulomb. From this he concluded that the charge on g an electron was numerically 1.6 x 10-19 coulomb.

j i mation Ltd. or a sealed container f light source b atomizer g viewing microscope

Visual Inf c oil droplets h charged metal plate (–) d charged metal plate (+) i ionizing radiation e charged oil droplets j power source © Diagram 19

Size and motion of ATOMIC STRUCTURE molecules Key words Brownian motion diffusion 1 Estimating the size of a molecule molecule g f

b 1 Estimating the size of h i k h a a molecule ● Scientists can estimate the size of a molecule by dividing the volume of a sphere by the volume of a cylinder. c ● In the example in the diagram, the volume of a spherical oil drop of

radius, rs, is given by: 3 4 x ␲ x rs j 3 ● When the oil drop spreads across the surface of water, it takes the shape of a r h e d cylinder of radius, c, and thickness, . The volume of such a cylinder is: Determining the radius of Determining the radius of an 2 ␲ x rc x h an oil drop oil drop spread ● If we assume that the layer of oil is one molecule thick, then h gives the 2 Brownian motion in air 3 Diffusion size of an oil molecule. ● When spread on water the drop of oil will have the same volume therefore: 3 h = 4 x ␲ x rs x 1 r 2 3 ␲ x rc 3 h = 4 rs 2 3 rc u x v 2 Brownian motion in air ● Brownian motion is the random l motion of particles through a liquid or gas. Scientists can observe this by w using a glass smoke chamber. n ● Smoke consists of large particles that can be seen using a microscope. ● In the smoke chamber, the smoke o m p q particles move around randomly due t to collisions with air particles. 3 Diffusion ● Diffusion is the spreading out of one s substance through another due to the random motion of particles. ● The diagram illustrates how scientists use a diffusion tube to observe this. a tape i wax-coated tray q glass smoke chamber b cardboard j lycopodium powder r glass diffusion tube Initially the color of the substance is mation Ltd.

c fine stainless steel wire k oil patch s liquid bromine capsule strongest at the bottom of the tube. or d magnifying glass l microscope t rubber stopper ● After a period of time, as a result of e 1/2 mm scale m removable lid u tap f view through magnifying n window v bromine capsule diffusion, the particles of the Visual Inf glass o lamp w rubber tube substance mix with air particles, and g oil drop p glass rod for converging x point at which pressure is the color becomes uniform down the h waxed sticks light applied to break capsule length of the tube. © Diagram 20

ATOMIC STRUCTURE Determination of Key words Avogadro’s constant anode mole Avogadro’s constant Determination of Avogadro’s constant electrolysis Faraday constant a b Defining Avogadro’s constant –+ ● Avogadro’s constant is the number of particles in a mole of a substance. It equals 6.023 x 1023 mol-1. ● It is F, the Faraday constant—96,500 coulombs per mole, the amount of electric charge of one mole of electrons—divided by 1.60 x 10-19 coulomb—the charge on one electron (expressed as e). ● Thus, the Avogadro constant, N, is A given by: N = F e or: 96,500 = 6.023 x 1023 mol-1 1.60 x 10-19

Determining the Constant ● The number of molecules in one mole of substance can be determined by using electrochemistry. ● During electrolysis, current (electron c flow) over time is measured in an electrolytic cell (see diagram). The number of atoms in a weighed sample is then related to the current to calculate Avogadro’s constant. Illustrating the Procedure d ● The diagram illustrates the electrolysis of copper sulfate. To calculate e Avogadro’s constant, the researcher weighs the rod to be used as the anode before submerging the two copper rods in copper sulfate. She then connects the rods to a power supply and an ammeter (an instrument used to measure electric current). She measures and records the current at regular intervals and calculates the average amperage (the f unit of electric current). Once she mation Ltd.

or turns off the current, she weighs the anode to see how much mass was lost. a power supply with ammeter b rheostat

Visual Inf Using the figures for anode mass lost, c hardboard or wooden electrode holder average current, and duration of the d copper rod cathode electrolysis, she calculates Avogadro’s e copper rod anode f copper sulfate solution © Diagram constant. 21

The mole ATOMIC STRUCTURE

Key words 1 Defining a mole atom ion molarity 1 particle – 6.023 × 1023 particles mole molecule

x amu x grams 1 Defining a mole ● Because atoms, ions, and molecules h ave very small masses, it is impossible 2 Moles of gas to count or weigh them individually. As a result, scientists use moles in a chemical reaction. ● A mole is the amount of substance that contains as many elementary entities (atoms, molecules, ions, any group of particles) as there are atoms in exactly 0.012 kilogram of carbon-12. This quantity is Avogadro’s constant (71 g) Cl 23 -1 2 H2 (2 g) (6.023 x 10 mol ). ● The significance of this number is that it scales the mass of a particle in atomic mass units (amu) exactly into grams (g). (44 g) CO ● Chemical equations usually imply that 2 22.4 liters N2 (28 g) the quantities are in moles. 2 Moles of gas ● One mole of any gas occupies 22.4 liters at standard temperature and (16 g) CH O (32 g) 4 2 pressure, (which is 0 ºC and atmospheric pressure). ● The diagram shows the mass in grams of one mole of the following gases:

chlorine (Cl2), carbon dioxide (CO2), methane (CH ), hydrogen (H ), 3 Molarity 4 2 nitrogen (N2), and oxygen (O2). 3 Molarity ● Molarity is concerned with the concentration of a solution. It indicates the number of particles in (127 g) FeCl NaOH (40 g) 2 1 liter of solution. ● A 1 molar solution contains 1 mole of a substance dissolved in water or some other solvent to make 1 liter of solution. 1 liter ● (95 g) MgCl2 Ca(NO3)2 (164 g) The diagram shows the mass in grams of one mole of the following

substances: iron(II) chloride (FeCl2), MgCl mation Ltd. magnesium chloride ( 2), barium or sulfate (BaSO4), sodium hydroxide NaOH Ca(NO )

( ), calcium nitrate ( 3 2), Visual Inf (233 g) BaSO4 KBr (119 g) and potassium bromide (KBr). © Diagram 22

ATOMIC STRUCTURE Atomic emission Key words spectrum: hydrogen atomic emission wavelength spectrum infrared Emission spectrum in the near ultra-violet and visible spectrum Balmer series ultraviolet Violet Red Atomic spectrum H° H␦ H␥ H␤ Hϰ ● The atomic emission spectrum of an element is the amount of electromagnetic radiation it emits when excited. This pattern of wavelengths is a discrete line spectrum, not a continuous spectrum. It is unique to each element. Investigating hydrogen ● Toward the end of the nineteenth century, scientists discovered that when excited in its gaseous state, an element produces a unique spectral pattern of brightly colored lines. Hydrogen is the simplest element and, therefore, was the most studied. Hydrogen has three distinctively observable lines in the visible spectrum—red, blue/cyan, and violet. 7.309 6.907 6.167 4.568 a Series Schematic series ● In 1885 Swiss mathematician and 30 6 0.6 physicist Johannes Jakob Balmer proposed a mathematical relationship for lines in the visible part of the hydrogen emission spectrum that is now known as the Balmer series. ● The series in the ultraviolet region at a shorter wavelength than the Balmer series is known as the Lyman series. ● The series in the infrared region at the longer wavelength than the Balmer series is known as the Paschen series. ● The Brackett series and the Pfund series are at the far infrared end of the hydrogen emission series. mation Ltd. or b a c d e f

Visual Inf a frequency (×1014Hz) d Paschen series b Lyman series e Bracket series c Balmer series f Pfund series © Diagram 23

Energy levels: hydrogen ATOMIC STRUCTURE atom Key words ground state orbital Energy-level schematic quantum number shell n = ? ultraviolet

n = 5 Energy levels ● Electrons are arranged in definite n = 4 energy levels (also called shells or orbitals), at a considerable distance from the nucleus. n = 3 ● Electrons jump between the orbits by emitting or absorbing energy. ● The energy emitted or absorbed is equal to the difference in energy between the orbits. Energy levels of hydrogen ● The graph shows the energy levels for n = 2 the hydrogen atom. Each level is described by a quantum number (labeled by the integer n). ● The shell closest to the nucleus has the lowest energy level. It is generally termed the ground state. The states farther from the nucleus have successively more energy. y g r

e Transition from n level to n E ground state ␥␤␣ ● Transition from n=2 to the ground state, n=1: Frequency =24.66 x 1014 Hz ● Transition from n=3 to the ground state, n=1: Frequency =29.23 x 1014 Hz ● Transition from n=4 to the ground state, n=1: Frequency =30.83 x 1014 Hz Ground state n = 1 Line spectrum ● This radiation is in the ultraviolet Line spectrum region of the electromagnetic spectrum and cannot be seen by the human eye. mation Ltd. or

␥ ␤␣ Visual Inf 30.83 29.23 24.66 Frequency / 1014 Hz © Diagram 24

ATOMIC STRUCTURE Luminescence

Key words 1 Luminescence fluorescence luminescence Energy phosphorescence levels Second E3 excited n = 3 state

1 Luminescence ● Luminescence is the emission of light caused by an effect other than heat. ● Luminescence occurs when a

substance is stimulated by radiation ) E and subsequently emits visible light. ( First y excited g E2 n = 2 ● The incident radiation excites r e state n

electrons, and as the electrons return E to their ground state, they emit visible light. Photon ● If the electrons remain in their excited state and emit light over a period of Photon time, the phenomenon is called phosphorescence. ● If the electrons in a substance return Ground to the ground state immediately after E1 state n = 1 excitation, the phenomenon is called Electron Electron fluorescence. absorbs emits photon photon 2 Fluorescence ● In this diagram, a fluorescent light tube contains mercury vapor at low pressure. Electrons are released from 2 Fluorescence hot filaments at each end of the tube and collide with the mercury atoms, exciting the electrons in the mercury atoms to higher energy levels. As the electrons fall back to lower energy states, photons of ultraviolet light are filament visible light filament emitted. ● The ultraviolet photons collide with atoms of a fluorescent coating on the inside of the tube. The electrons in these atoms are excited and then return to lower energy levels, emitting ultraviolet visible light. e– photons are emitted e– mation Ltd. or mercury fluorescent atoms coating Visual Inf © Diagram 25

Organizing the elements ELEMENTS AND COMPOUNDS

1 Antoine Lavoisier Key words Group 1 Group 2 Group 3 Group 4 atomic mass atomic volume heat sulfur copper lime element light phosphorus tin baryta oxygen lead magnesia nitrogen zinc alumina 1 Antoine Lavoisier silica ● In 1789, French chemist Antoine Lavoisier organized what he believed 2 Johann Dobereiner were the elements into four groups: Group 1 gases, Group 2 non-metals, Triad Relative atomic mass Group 3 metals, and Group 4 earths. Li Na K 7 23 39 2 Johann Dobereiner S Se Te 32 79 128 ● In 1817, German chemist Johann Cl Br I 35.5 80 127 Dobereiner noticed that the atomic Ca Sr Ba 40 88 137 mass of strontium was about half way between that of calcium and barium. 3 John Newlands After further study, he found that he could organize other elements into H Li Be B C N O similar groups based on the same 1 2 3 4 5 6 7 relationship to each other. He called F Na Mg Al Si P S these groups triads. Subsequently, scientists attempted to arrange all of 8 9 10 11 12 13 14 the known elements into triads. Cl K Ca Cr Ti Mn Fe 15 16 17 18 19 20 21 3 John Newlands ● In 1864, English chemist John 4 Lothar Meyer Newlands noticed that if the elements were arranged in increasing order of 80 atomic mass, the eighth element after any given one had similar properties. He likened this to an octave of music and called the regularity the “law of octaves.” 60 ● Newlands’s arrangement worked well for the first 17 elements but broke

1 down thereafter. Consequently, it was – l o not well received by other scientists. m 3 m

c 4 Lothar Meyer / e 40 ● m In 1870, German chemist Lothar Meyer u l

o plotted a graph of atomic volume v c

i against atomic mass.

m ● o He found a pattern in which elements t

A of similar properties appeared in similar positions on the graph. 20 mation Ltd. or Visual Inf 0 0 5 10 15 20 25 3035 40 45 50 55 60

Atomic number © Diagram 26

ELEMENTS AND COMPOUNDS The periodic table

Key words 1 Part of Mendeleyev’s periodic table atomic mass noble gases atomic number period Group element periodic table group Period I II III IV V VI VII VIII group 1 1 H

1 Mendeleyev’s periodic 2 Li Be B C N O F table ● The modern periodic table is based on that developed by Russian chemist 3 Na Mg Al Si P S Cl Dmitry Mendeleyev in the 1860s. ● He arranged the elements in order of K Ca * Ti V Cr Mn Fe Co Ni increasing atomic mass. He called the horizontal rows periods and the 4 Cu Zn * * As Se Br vertical columns groups. He grouped the elements on the basis of their properties. Rb Sr Y Zr Nb Mo * Ru Rh Pd ● Mendeleyev made a separate group for those elements that did not appear to 5 Ag Cd In Sn Sb Te I fit the pattern. He also left spaces where there was no known element Spaces were left for elements that had not been discovered. They were candium, gallium, germanium, and technetium. that fit the pattern and made predictions about the missing elements. 2 Modern Periodic Table ● There were some problems with Mendeleyev’s table. For example, iodine was placed after tellurium on the basis Metals of its chemistry, even though its atomic mass was Semi-metals lower than tellurium. Also, there was no obvious place Non-metals for the noble gases. These 1 2 problems were subsequently H He resolved when, in 1914, 3 4 5678910 English physicist Henry Li Be B CNOFNe Moseley showed that the 11 12 13 14 15 16 17 18 Na Mg elements could be arranged Al Si P S Cl Ar in a pattern on the basis of 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr their atomic number. 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 2 The modern Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 55 56 57- 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 periodic table Cs Ba 71 Hf Ta W Re Os Ir - Pt Au Hg Tl Pb Bi Po At Rn ● Metals occupy positions to 87 88 89- 104 105 106 107 108 109 110 111 112 113 114 115 116 Fr Ra 103 Uub Uut Uuq Uup Uuh the left and center, while - Rf Db Sg Bh Hs Mt Ds Rg non-metals are found to the right. Hydrogen is the 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 exception to this pattern. La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu The atomic structure of 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103

mation Ltd. Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

or hydrogen would indicate that it belongs at the top left

Visual Inf of the table; however, it is a non-metal and has very different properties from

First ionization energies ELEMENTS AND COMPOUNDS of the elements Key words electron lanthanide series element mole group 1 nucleus ion period 0 0 0 0 0 r r e e n e 7 8 2 5 7 3 1 0 3 5 ionization energy shell 1 K 2 1 1 A X 2 R H N 0 0 0 l 0 t r 1 5 8 4 I First ionization energy F 1 0 2 6 C 1 A 1 B 1 1 ● The first ionization energy of an

0 element is the energy needed to 0 0 0 0 e o 1 e 0 1 7 4 3 S O 0 8 8

9 remove a single electron from 1 mole 1 T P 1 S of atoms of the element in the gaseous 0 0 i 0 0 0

s state, in order to form 1 mole of b 1 0 5 3 0 0 P 4 N 9 8 7 B 1 1

A positively charged ions. S ● Reading down group 1, there is a 0 i 0 0 0 e 0 b n decrease in the first ionization 9 1 2 9 6 C 0 7 7 7 7 S 1 S P G energies. This can be explained by considering the electronic l l 0 0 0 0 0 a

n configuration of the elements in the 8 8 0 6 9 B I T 5 5 5 5 8 A G group. Reading down, the outer electron is further from the positively 0 0 0 g d n 1 1 7 charged nucleus, and there is an 0 9 8 1 Z C H increasing number of complete shells of inner electrons, which to some 0 0 0 g u u 9 3 5 7

7 extent, shield the outer electron from 8 C A A the nucleus. The result is that less i

t energy is needed to remove the outer 0 0 0 d 7 0 4 7 8 8 N P electron. A similar situation exists in P other groups. 0 0 0 o h r 8 2 6 I 7 7 8 Increase in ionization C R energy 0 s 0 0 u ● e There is a general increase in the first 1 4 6 7 7 8 F O R ionization energies across a period. This increase is due to electrons at the n 0 0 0 e c 2 6 0 same main energy level being attracted 7 7 7 T R M by an increasing nuclear charge. This charge is caused by the increasing o r 0 0 0 7 5 8 number of protons in the nucleus. The 7 W 6 6 C M increase makes it progressively more difficult to remove an electron; thus 0 0 0 b a 5 6 6 V 7 6 6 more energy is needed. T N ● The diagram illustrates this principle f i 0 0 0 r using the first six periods minus the 8 6 6 T 6 6 6 Z H lanthanide series. 0 0 0 Elements whose ionization c a 2 3 4 Y 5 6 6 L

S energies are the greatest in their period g 0 0 r 0 0 0 a e a He Helium 5 0 9 0 4 7 5 5 5 9 mation Ltd. S C B B Ne Neon M Ar Argon or 0 i 0 0 0 0 0 a s

b Kr Krypton 1 8 2 2 0 0 3 Visual Inf H K L 3 5 4 5 4 1

C Xe Xenon R N Rn Radon 1 3 2 5 6 4 © Diagram 28

ELEMENTS AND COMPOUNDS Variation of first Key words ionization energy ionization energy noble gases period 2,500 periodicity shell a = 2,370

First ionization energies ● The graph shows a repeating pattern, or periodicity , corresponding to b = 2,080 reading down the periods of the periodic table. 2,000 ● Within a period, it becomes increasingly more difficult to remove an electron due to the increasing nuclear charge. The graph peaks at the last element in each period, which is a noble gas (labeled on the graph). ● The noble gases have complete outer shells of electrons. This electron configuration provides great stability, c = 1,500 1

and consequently, the noble gases are – l 1,500 o

very unreactive. Some are totally m

unreactive. The first ionization J K

/ d = 1,350 energies of the noble gases are very y g r

high. e n e n o i t e = 1,170 a z i n o i t s r i f F 1,000

500

mation Ltd. 0 or 0 10 20 30 40 50 60 70 80 90 Atomic number

Visual Inf a Helium d Krypton b Neon e Xenon c Argon f Radon © Diagram 29

Melting points of the ELEMENTS AND COMPOUNDS elements °C Key words group noble gases group 1 period lanthanide series solid liquid transition metals 8 0 7 9 2 1 r r e e n e 7 1 5 4 8 7 1 1 1 2

2 melting point – – – – – K A – X R H N 1 0 l t 4 r 4 7 0 2 1 I 0 Melting points 1 – F 2 1 3 C – A B – ● The melting point is the point at which the solid and liquid phase of a 8 4 0 7 9 e o 1 e 1 5 1 5 2 S 1 O 2

2 substance is in equilibrium at a given 4 T – P S pressure. ● 0 i 1 1 In a solid , the particles are held in a 7 s b 4 7 1 3 7 2 4 P N 2 8 6 B

– rigid structure by the strong forces of A S attraction that exist between them. 0 0 i 7 2 8 e b n They vibrate but cannot move 1 0 3 2 3 7 4 C 9 2 3 S 1 3 S P G position. When a solid is heated to its melting point, the particles gain 0 l l 4 0 6 a 0 0

n sufficient energy to overcome these 6 0 5 3 3 B 1 I T 3 6 A 2 G forces of attraction, and the particles are able to move position. 1 0 9 g d n

2 ● 2 3 Within groups of metallic elements, 3 – 4 Z C H the melting point decreases down the group. The converse is true for non- 3 4 2 g u u 8 6 6 0 0 metals, where the melting point 9 1 1 C A A increases down the group. ● 5 4 i 2 Reading across periods 2 and 3, the t d 5 7 5 7 5 4 P N 1 elements follow a pattern of metallic 1 1 P structure, giant covalent structure, and 6 5 0 h o simple covalent structure. The melting 1 r 6 9 4 4 9 I 1 2 1 C R point increases until a maximum is reached with the element that exists as 0 5 0 s u 1 e 3 0 a giant covalent structure. 3 7 5 F 1 2 2 O R ● The more reactive metals in group 1 are soft and have low melting points. 0 4 2 n e c 7 8 4 Transition metals (elements that have 1 1 2 T 2 1 3 R M an incomplete inner electron structure) are generally harder and 7 0 0 o r 1 1 5 4 6

8 have higher melting points. W C 1 3 2 M ● The noble gases exist as single atoms 6 7

0 with only weak forces of attraction b 9 6 a 9 9 4 V 8 between them. Consequently, their T 2 1 2 N melting points are very low. 7 2 0 ● f i

r Using the first six periods minus the 2 5 6 2 8 6 T Z H 2 1 1 lanthanide series, the diagram highlights the element with the 1 2 1 c a 4

2 highest melting point in a period. 2 5 Y 5 9 1 1 L S Elements whose melting points 8 g 9 9 5 r 9 e a a are the greatest in their period 7 3 2 4 6 2 7 7 8 6 mation Ltd. S 1 C B B

M C Carbon or Si Silicon 9 i 1 a s b 9 5 3 8 9 V Vanadium 8 2 Visual Inf 2 3 6 9 H K 1 L – C R N Mo Molybdenum W Tungsten 1 3 2 5 6 4 © Diagram 30

ELEMENTS AND COMPOUNDS Variation of melting Key words points element melting point a e period periodicity periodic table

Melting points 3,000 ● The graph shows a repeating pattern, or periodicity , corresponding to reading down the periods of the periodic table. ● The structure of periods 2 and 3 d with regard to the nature of the elements, is: 2,500 Elements having a metallic structure: melting point increasing Elements having a giant covalent structure: melting point maximum Elements having a simple covalent structure: melting point decreasing 2,000 c ● In general, the melting point increases at the start of these periods, corresponding to elements that have C metallic structure. The melting point is ° t n i

at maximum for elements that have a o p

giant covalent structure (labeled on g n

i 1,500 t

the graph). After this, the melting l e b

point rapidly falls to low values, M corresponding to those elements that have a simple covalent structure.

1,000

500

0 mation Ltd. or 0 10 20 30 40 50 60 70 80 90 Atomic number a Carbon Visual Inf b Silicon c Vanadium d Molybdenum

Boiling points of the ELEMENTS AND COMPOUNDS elements °C Key words boiling point lanthanide series gas liquid group noble gases group 1 transition metals 9 6 6 2 r 2 r e e n e 6 4 5 8 6 1 1 2 2 kinetic energy – – – – K A – X R H N 8 l t 7 r 5 4 9 8 3 I 3

8 Boiling points 1 F 5 1 3 – C A – B ● The boiling point is the temperature at which a liquid becomes a gas. 3 2 5 5 0 e o e 8 6 4 8 9 1

S ● O 9 4

6 The particles in a liquid are held 9 T – P S together by the strong forces of 6 0 0 i

0 attraction that exist between them. 3 s b 9 6 5 1 8 1 7 P 5 N 6 2 B 1 – 1 The particles vibrate and are able to A S move around, but they are held closely 7 0 0 0 0 i e b n 2 together. When a liquid is heated to its 2 3 6 4 8 2 6 8 7 C S 1 4 2 2 2 S P G boiling point, the particles gain kinetic energy, moving faster and faster. 3 0 7 0 7 l l a 6 8 5 0 5

n Eventually, they gain sufficient energy 4 5 4 4 0 B I T A 1 2 2 2 2 G to break away from each other and exist separately. There is a large 7 7 5 g d n 5 0 6 increase in the volume of any 3 7 9 Z C H substance going from a liquid to a gas. ● Within groups of metallic elements, 7 0 2 g u u 1 6 8 2 5 0 the boiling point decreases down the 2 2 3 C A A group. The converse is true for non- 7 0 0 i metals: the melting point increases t d 2 7 3 8 9 7 P N down the group. 3 2 2 P ● The more reactive metals in group 1 7 0 0 h o have relatively low boiling points. 2 7 r 3 1 7 8 I 3 4 2 C R Transition metals generally have very high boiling points. 7 0 0 s

u ● 9 e 0 5 The noble gases exist as single atoms 2 7 9 F 5 2 O 3 R with only weak forces of attraction between them. Consequently, their 7 7 2 n e 7 2 c 6 boiling points are very low because it 8 6 9 T 1 4 5 R M takes relatively little energy to overcome these forces. 0 0 0 o r 2 7 6 ● 6 4 5 Using the first six periods minus the W C 2 5 5 M lanthanide series, the diagram 7 0 2 highlights the element with the b 2 a 8 4 7 4 3 V highest boiling point in a period. T 4 5 3 N 2 7 7 Elements whose boiling points f i r 0 7 8 3 2 6 are the greatest in their period T Z H 4 3 4 C Carbon 1 7 8 Si Silicon c 3 5 a 3 8 4 3 Y V Vanadium 2 L 3 S 3 Mo Molybdenum 0 0 4 4

7 Re Rhenium g r e a a 7 4 8 8 0 9 1 3 6 4 mation Ltd. S 1 1 1 1 2 C B B M or 3 2 9 i 3 6 a 0 s b 5 4 6 8 8 6 2 Visual Inf H 3 K L 6 7 8 6 – 1 C R N 1 3 5 2 6 4 © Diagram 32

ELEMENTS AND COMPOUNDS Variation of boiling Key words points boiling point gas group 1 group 2 c d e transition metals a

Variation of boiling point ● The majority of non-metallic elements are gases at room temperature and 3,000 atmospheric pressure. Most non- metallic elements have simple covalent structures and have very low boiling points. b ● Elements with metallic and giant covalent structures have very high 2,500 boiling points (see diagram). The boiling points of transition metals are generally much higher than those of the group 1 and group 2 metals.

2,000 C ° t n i o p g n i l i o

B 1,500

1,000

500

0 mation Ltd. or 0 10 20 30 40 50 60 70 80 90 a Carbon Atomic number Visual Inf b Silicon c Vanadium d Molybdenum

Atomic volumes of the ELEMENTS AND COMPOUNDS elements Key words atomic mass group 8 atomic volume lanthanide series density mole element noble gases 5 2 2 9 8 8 r r e . e . . . n . . e 1 2 2 0 4 6 group period 3 1 2 3 4 5 K A X R H N l 6 6 7 1 t r . . . . I 7 5 5 Atomic volume 8 F 1 1 C 2 2 A B ● The atomic volume is the volume of

3 one mole of the atoms of an element. 4 5 5 0 . 2 e . . . o e . 0 5 6 4 S 2 O 1

1 It can be found by dividing the atomic 1 2 T P S 2 mass of one mole of atoms by the 1 i 2 9 4 3 density of the element: s . . . . b . 1 3 7 6 8 P N 1 1 1 1 2

B Atomic volume = Atomic mass A S Density 3 i 3 4 23 6 ● e 4 . b n . .

. Since there are 6.023 x 10 atoms per . 1 3 8 6 C 5 1 S 1 1 1 S P G mole of atoms, it would seem possible to use the atomic volume to calculate l l 0 8 8 2 a 3 . . . . .

n the volume of a single atom, and thus 7 1 5 0 B 4 1 1 I T 1 1 A G its radius. However there are two problems with doing this. First, the 8 0 g 2 d n . . . 3 4 state of an element, and therefore its 9 1 1 Z C H density, changes with temperature and pressure. Second, using the atomic 3 2 g u 1 u . . . 0 0 7 volume to calculate the volume of a 1 1 C A A single atom assumes that an element

i consists of atoms that are not bonded t 1 6 8 d . . . 9 6 8 N P to each other. This is true only of the P group 8 elements (noble gases). For 3 6 o 6 h these reasons, it is not possible to r . . . I 8 8 6 C R consider the volume of an atom in isolation, but only as part of the s 1 5 1 u . e . . structure of an element. 7 8 8 F O R ● In general, atomic volume increases down a group. Across a period, it n e 9 5 4 c . . . decreases and then increases. 7 8 8 T R M ● The diagram highlights the element with the highest atomic volume in the o r 6 4 3 . . . 7 9 9 first six periods (minus the lanthanide W C M series). 9 9 b . 9 . a . 0 0

V Elements with peak atomic 8 1 1 T N volumes He Helium f 5 i 6 2 r . . . 3 4 0 K Potassium T 1 1 1 Z H Rb Rubidium Cs Cesium 6 1 7 . . c . a 2 6 4

Y Rn Radon 1 1 2 L S 2 0 0 g 0 r a e a . . . 9 . . 9 4 6 4 4 1 3 mation Ltd. S 2 3 C B B M or 1 9 7 7 0 i 0 a . s . . . b . . 1 4 5 3 4 3 Visual Inf H K 1 L 7 1 2 5 4 C R N 1 3 5 2 6 4 © Diagram 34

ELEMENTS AND COMPOUNDS Variation of atomic Key words volumes atomic mass atomic number 70 d atomic volume periodicity

Periodicity ● As early as the Middle Ages, scientists recognized that elements could be 60 differentiated by their properties and that these physical and chemical c properties were periodic. ● The German chemist Lothar Meyer demonstrated periodicity by plotting atomic volumes against atomic e weights (the term atomic mass is now 50 used). ● This periodicity is better shown by b plotting atomic volumes against atomic number. ● You can see periodicity most clearly by 1

the pattern between potassium (b) – l

o 40 and rubidium (c), and between m rubidium (c) and cesium (d) in the 3 m c

diagram. These correspond to the e m

changing values across period 4 and u l o

period 5, respectively. v c

i a m o t

A 30

mation Ltd. 0 or 0 10 20 30 40 50 60 70 80 90 Atomic number a Helium

Visual Inf b Potassium c Rubidium d Cesium e Radon © Diagram 35

Atomic mass ELEMENTS AND COMPOUNDS

Key words 1 Carbon-12 atomic mass isotope

12 ( 6C) 1 Carbon-12 ● To compare the masses of different atoms accurately, scientists need a standard mass against which all other masses can be calculated. Masses are given relative to this standard. + ● The isotope carbon-12 is used as the + + standard. On this scale, atoms of + carbon-12 are given a mass of exactly + + 12. The atomic masses of all other atoms are given relative to this standard. ● If an element contained only one isotope, its atomic mass would be the relative mass of that isotope. However, most elements contain a mixture of several isotopes in varying proportions. ● Natural abundance gives the proportion of each isotope in a sample of the element. ● If more than one isotope of an element is present, the atomic mass is calculated by taking an average that 2 Lithium takes into account the relative proportion of each isotope. Diagrams Isotope Natural abundance 2 and 3 illustrate how the atomic mass Lithium-6 (6Li) 7.5% of common isotopes of lithium and 3 chlorine would be calculated.

7 Lithium-7 (3Li) 92.5% 2 Lithium ● There are two common isotopes of The relative atomic mass of lithium is given by: lithium: lithium-6 and lithium-7. ● The atomic mass of lithium is 6.925, (6 × 7.5) + (7 × 92.5) = 6.925 but for most calculates a value of 7 is 100 sufficiently accurate. 3 Chlorine 3 Chlorine Isotope Natural abundance ● There are also two common isotopes of chlorine: chlorine-35 and chlorine- 35 Chlorine-35 (17Cl) 75.77% 37. ● The atomic mass of chlorine is 37 24.23% 35.4846, but for most calculations a Chlorine-37 (17Cl) mation Ltd.

value of 35.5 is sufficiently accurate. or ● Rounding the atomic mass of chlorine The relative atomic mass of lithiumis given by:

to the nearest whole number would Visual Inf (35 × 75.77) + (37 × 24.23) lead to significant errors in = 35.4846 100 calculations. © Diagram 36

ELEMENTS AND COMPOUNDS Periodic table with Key words masses and numbers atomic mass atomic number element isotope 9 0 5 8 0 2 1 0 r . 8 9 r e e n . e 6 . . 6 0 4 1 0 8 2 . 2 3 3 8 5 0 9 1 1 3 A K 2 4 H R X N 3 2 8 1 0 0 5 0 7 9 . r l 9 4 0 t 0 9 Atomic mass 2 5 5 3 3 . . r . . 6 7 1 I 1 u 9 F 6 3 8 5 5 9 1 0 B 9 2 C 4 7 2 A L 2 L 1 1 7 1 ● 3 The atomic mass of an element is the 7 1

average of the relative masses of its 0 6 6 4 6 0 h . 2 9 0 0 e 6 4 0 9 e 4 2 o 2 . 0 . o b 7 . 0 6 1 9 1 8 .

isotopes. It provides the relative mass u 8 5 3 S 5 2 8 O 0 1 1 3 2 7 T 2 2 S 6 P 2 1 Y N 1 7 3 7 1 U

of an “average” atom of the element, 1 8 6 7 2 3

which is useful for calculations. 1 p 9 7 8 . i 9 . 9 9 5 3 s 8 0 d 3 1 1 b . . . u 9 1 8 . 5 7 1 8 m

● 8 5 P 3 N 5 0 0 4 8 The atomic mass is represented by the 1 1 B 2 6 2 4 A S 0 2 1 M 1 7 3 T U 1 6 2 symbol A(r) 1 0 1 8 4 6 ● 1 q 7 2

The atomic mass of an isotope is its 9 . . 0 6 i 4 2 b 2 2 7 e n r 0 0 0 . . . 8 8 . u 6 4 1 7 m 8 3 8 5 C 5 0 2 8 7 1 1 6 S 1 2 2 P E S mass relative to the isotope carbon-12. 0 G 1 2 F 1 7 2 1 6 U 2 ● The atomic mass of an isotope is the 1 8 2 3 2 0 1 t 3 8 4 . . 7 9 l 0 sum of the protons and neutrons in its l 2 8 3 a 1 9 1 o . . s . 7 9 . 8 n u 5 3 4 4 1 5 B 3 4 8 9 I 4 7 1 6 9 2 1 1 T 0 A 0 G H E 2 1 6 2 1 nucleus. 6 U 2 1 ● The atomic masses of the elements are 9 1 1 0 b 5 4 5 . . 4 5 1 2 n y 0 8 g 0 d . f . 8 6 presented below the element on the u 8 0 2 1 5 3 4 8 5 2 9 6 2 1 1 Z 0 D C H 2 C 1 6 U 6

periodic table at right. 2 1 0 7 2 5 9 . 9 2 5 9 7 1 . 7 u 9 9 g g u b . . k 7 5 6 Atomic number 7 1 4 6 2 4 7 3 8 9 6 1 2 0 A R T C A 2 9 B 1 6 5

● 1 The atomic number of an element is 1 2 8 9 5 the number of protons in its nucleus. 4 . 0 1 i s 6 t 2 7 0 6 . 8 8 d . . 6 4 6 7 d m 1 4 5 ● 2 4 7 7 8 9 6

The atomic number is usually 1 2 P 0 N D P 2 9 5 1 5 C G 1 represented by Z. 1 0 2 3 9 ● 6 t . 8

The number of neutrons in the 2 9 9 3 5 . 7 h o 9 7 r u . 5 3 m 2 6 . 0 4 I 2 2 4 7 1 8 9 6 1 M 2 0 C R E

nucleus of an isotope is: 2 9 A 5 1 5 1 A(r) – Z 1 7 3 6 4 0 2 7 8

● 3 . s s 8 4 . 4 6

The atomic numbers of the elements u 6 e . u 4 . 2 1 7 m 0 4 0 2 4 7 0 9 5 6 2 1 F 0 H O R P 2 9 S 5 1 are presented above the element in 5 1 1 the periodic table at right. 1 0 0 4 4 2 7 0 n 0 9 c 7 h e . 3 5 5 p . . 3 . 1 6 m 0 3 6 2 4 7 5 8 9 4 6 1 2 T B R 2 M 8 N P 4 9 5 1 1 3 4 4 0 4 6 8 0 6 o 2 r g 9 0 . 4 2 . 4 . d 2 0 . . 6 0 3 2 7 4 8 4 9 5 U 6 2 1 S W 2 C M 8 3 N 4 9 5 1 1 2 5 1 3 4 1 9 2 5 9 b 9 b 0 9 . a r 1 3 3 . a 1 . . . 9 6 0 0 2 4 7 V 1 0 9 2 5 0 1 2 T D P N P 8 3 4 9 5 1 1 2 4 9 2 7 2 1 1 4 0 e r f 4 f i 8 . . . 0 2 2 2 0 h 8 . 6 . 0 2 8 2 4 7 0 9 Z 5 1 7 C T 2 H R 1 T 7 3 4 9 4 1 1 2 3 1 0 6 0 0 7 9 9 9 7 1 1 9 . c 9 . a c . 7 – 2 – 2 3 8 Y 8 4 5 8 7 L 2 9 A S 3 4 8 5 1 8 8 3 2 1 1 6 3 a g 0 r 3 6 a 8 0 8 a e . 6 . . . 0 2 4 2 . 2 8 3 7 5 1 7 0 4 S R mation Ltd. 2 C B B 9 M 3 8 4 2 or 1 0 0 7 8 0 4 9 3 s r i 4 1 a 0 7 b 0 . 7 5 . . . 9 9 1 3 2 1 . K Visual Inf 8 2 1 3 H 5 0 1 F L 5 3 9 C . 2 N R 6 3 3 2 8 1 1 © Diagram 37

Calculating the molecular ELEMENTS AND COMPOUNDS mass of compounds Key words atomic mass ionic compound covalent lattice 1 Diatomic molecule (chlorine) compound molecular mass diatomic molecule

Calculating molecular mass chlorine You calculate the molecular mass of a compound the same way regardless of structure: Cl = 35.45 1. Multiply the number of atoms in an element by its atomic mass. 2. Repeat this process for each element in the compound, then 3. Add the numbers. 2 Covalent compound (ethanol) 1 Diatonic molecule (chlorine) ● The element chlorine exists as a

diatomic molecule Cl2. Atomic mass of chlorine = 35.5 hydrogen Molecular mass of chlorine = 2 x 35.5 = 71 carbon 2 Covalent compound (ethanol) H = 1 C = 12 ● Ethanol is a simple covalent O = 16 oxygen compound that has the formula

C2H5OH. Atomic mass of carbon = 12; hydrogen = 1; oxygen = 16. Molecular mass of ethanol = (2 x 12) + (6 x 1) + (1 x 16) = 46 3 Ionic compound (sodium chloride) 3 Ionic compound (sodium chloride) ● Ionic compounds do not exist as molecules but as a giant lattice chlorine composed of ions in a fixed ratio. The formula mass of an ionic compound is the sum of the atomic masses of the ions in their simplest ratio. ● Sodium chloride consists of an ionic lattice in which the ions are present in sodium the ratio 1:1. Therefore, the formula of sodium chloride is taken to be NaCl. Atomic mass of sodium = 23; chlorine = 35.5. Formula mass of sodium chloride

= 23 + 35.5 = 58.5 mation Ltd. or Visual Inf Na = 23.00 Cl = 35.45 © Diagram 38

ELEMENTS AND COMPOUNDS Structure of some ionic Key words crystals anion ionic crystal bond ion cation lattice 1 Simple cubic structure (CsCl) cations coordination number anions

Ionic crystals ● In an ionic crystal, each ion is surrounded by a number of oppositely charged ions in a lattice structure. ● There are several types of ionic structures. Simple: The atoms form grids. Body centered: One atom sits in the center of each cube. Face centered: One atom sits in each “face” of the cube. ● The lattice structure is determined by two factors: 1. the ratio of the number of cations (positively charged ions) to anions 2 Face-centered cubic structure (NaCl) cations (negatively charged ions) anions 2. the ratio of the radii of the ions. ● In general, the higher the value of the radius ratio the higher the coordination number of the lattice. The coordination number is the number of atoms, ions, or molecules to which bonds can be formed. 1 Simple cubic structure (CsCl) ● In cesium chloride, the radius ratio is 0.94 (due to the large cesium ion). The coordination is 8:8. Each ion is surrounded by 8 oppositely charged ions. 3 Body-centered cubic structure (CaF2) cations 2 Face-centered cubic structure (NaCl) anions ● The radius ratio in the sodium chloride lattice is 0.57. The coordination is 6:6. Each ion is surrounded by 6 oppositely charged ions. 3 Body-centered cubic structure (CaF2) ● In calcium fluoride the radius ratio is mation Ltd.

or 0.75. The coordination is 8:4. Each calcium ion is surrounded by 8

Visual Inf fluoride ions, while each fluoride ion is surrounded by 4 calcium ions. © Diagram 39

Crystal structure of ELEMENTS AND COMPOUNDS metals: lattice structure Key words body centered hexagonal close cubic packing packing 1 Hexagonal close packing crystal lattice face-centered unit cell cubic close packing

Metallic crystals ● Like all other crystals , metallic crystals are composed of unit cells, sets of atoms, ions, or molecules in orderly three dimensional arrangements called lattices. 1 Hexagonal close packing ● When arranged in a single layer, the most efficient method of packing the ions is in the form of a hexagon in which each ion is surrounded by six other ions. ● In hexagonal close packing, a second layer is positioned so that each ion in 2 Face-centered cubic close packing the second layer is in contact with three ions in the first layer. The third layer is placed directly above the first, and the fourth layer directly above the second, etc. This arrangement is sometimes represented as ABABAB. 2 Face-centered cubic close packing ● Here the third layer does not sit directly above either the first or second layers. The pattern is repeated after three layers, giving rise to an ABCABCABC arrangement. 3 Body-centered cubic packing 3 Body-centered cubic packing ● Here the layers are formed from ions arranged in squares. The second layer is positioned so that each sphere in the second layer is in contact with four spheres in the first layer. The third layer sits directly above the first layer, giving rise to an ABABAB arrangement. mation Ltd. or Visual Inf © Diagram 40

ELEMENTS AND COMPOUNDS Crystal structure of Key words metals: efficient packing body-centered hexagonal close cubic packing packing coordination 1 Efficient packing number face-centered Hexagonal close packing cubic close packing

1 Efficient packing ● Both hexagonal close packing and face-centered cubic close packing may be considered as efficient packing since the spheres occupy 74 percent of the available space. In both arrangements, each sphere is in contact with 12 others, and is said to have a coordination number of 12. 2 Less efficient packing ● Body-centered cubic packing is less efficient than hexagonal and face- centered cubic close packing. Spheres Face-centered cubic close packing occupy only 68 percent of the available space. Each sphere is in contact with eight others (four in the layer above and four in the layer below) and, therefore, has a coordination number of eight. Metals showing hexagonal close packing ● Cobalt ● Magnesium ● Titanium ● Zinc Metals showing face- centered cubic close packing ● Aluminum 2 Less efficient packing ● Calcium Body-centered cubic packing ● Copper ● Lead ● Nickel Metals showing body- centered cubic packing ● Group 1 metals ● Barium mation Ltd. ● Chromium or ● Iron ● Vanadium Visual Inf © Diagram 41

Chemical combination: ELEMENTS AND COMPOUNDS ionic bonding Key words anion noble gases bond oxide 1 Formation of sodium chloride (NaCl) cation shell chloride ionic bonding

Ionic bonding ● Ionic bonds are formed by the attraction of opposite charges. ● In ionic bonding, the atoms in a compound gain, lose, or share electrons so the number of electrons in their outer shell is the same as the Sodium atom (Na) Chlorine atom (Cl) nearest noble gas on the periodic table. ● Non-metals gain electrons to give negatively charged ions (anions). ● Metal atoms loose electrons to give positively charged ions (cations). 1 Formation of sodium chloride (NaCl) ● A sodium atom has one electron in its outer shell. The easiest way it can attain a complete outer shell is by Chlorine ion (Cl–) Sodium ion (Na+) losing this electron to form a sodium ion, Na+. ● A chlorine atom has seven electrons in its outer shell. The easiest way it can attain a complete outer shell is by gaining one more electron to + Na form a chloride ion, Cl-. Na Cl Cl– 2 Formation of Sodium chloride magnesium oxide (NaCl) (MgO) ● A magnesium atom has two electrons in its outer shell. It loses these electrons to form a magnesium ion, Mg2+. ● An oxygen atom has six electrons in its 2 Formation of magnesium oxide (MgO) outer shell. It gains two electrons to form an oxide ion, O2-.

Electronic configuration Na (sodium atom) 2.8.1 2– Mg O O Na+ (sodium ion) 2.8

Cl (chlorine atom) 2.8.7 mation Ltd. or Cl- (chloride ion) 2.8.8 Mg (magnesium atom) 2.8.2 Visual Inf Mg2+ (magnesium ion) 2.8 Magnesium ion (Mg2+) Oxygen ion (O2–) Magnesium oxide O (oxygen atom) 2.6 O2- (oxide ion) 2.8 © Diagram 42

ELEMENTS AND COMPOUNDS Chemical combination: Key words ionic radicals carbonate resonance ion structure limiting form sulfate 1 Carbonate ion nitrate radical

Radicals – – 2– O O O O ● A radical is a group of atoms that – cannot be represented by one O C O C O C O C structural formula. It can pass O O – O O unchanged through a series of – chemical reactions. Radicals include CO 2- resonance the carbonate ion, 3 , the nitrate limiting structure - 2- ion, NO3 , and the sulfate ion, SO4 . forms 1 Carbonate ion ● The carbon atom is bonded to three oxygen atoms. By transferring electrons, it is possible to write three limiting forms for this ion. (Limiting forms are the possibilities for the 2 Nitrate ion distribution of electrons in a molecule or ion.) ● Electrons are continually being transferred in the ion. Thus its exact – – form is constantly changing. The ion is O O O O – best represented as a resonance O N O N O N O N structure (the average of the limiting – forms) in which dotted lines indicate O O O O that the charge on the ion, 2-, is spread over all three of the limiting resonance forms structure carbon–oxygen bonds. 2 Nitrate ion ● The nitrogen atom is bonded to three oxygen atoms. This ion has three limiting forms. ● It is best represented as a resonance structure in which dotted lines indicate that the charge on the ion, 1-, 3 Sulfate ion is spread over all three of the nitrogen–oxygen bonds.

3 Sulfate ion – – – – 2– O O O O O O O O O O ● The sulfur atom is bonded to four oxygen atoms. This ion has three S S S S S limiting forms. O O O O O O O O O O ● The ion’s exact form is constantly – – – changing. It is best represented as a resonance mation Ltd.

or resonance structure in which dotted limiting structure lines indicate that the charge on the forms

Visual Inf ion, 2-, is spread over all four of the sulfur–oxygen bonds. © Diagram 43

Chemical combination: ELEMENTS AND COMPOUNDS covalent bonding Key words ammonia methane bond nitrogen 1 The hydrogen molecule carbon shell hydrogen ionic compound

Covalent bonding ● Atoms gain stability by having a complete outer shell of electrons. In 2 hydrogen hydrogen ionic compounds, this is achieved by atoms molecule (H2) the transfer of electrons. In covalent bonding, atoms share electrons. 3 The ammonia molecule 1 The hydrogen molecule ● A hydrogen atom has one electron in its outer shell. In a hydrogen molecule, two hydrogen atoms each donate this electron to form a bond. Each hydrogen atom can be thought of as having control of the pair of electrons in the bond. Thus, each can be thought of as having a full outer shell of electrons. The single bond is shown as H-H. 2 The ammonia molecule ● A nitrogen atom has five electrons in nitrogen 3 hydrogen ammonia its outer shell and needs another three atom atoms molecule (NH ) 3 electrons to complete the shell. In ammonia, three hydrogen atoms each donate one electron to form three N-H 4 The methane molecule bonds. The nitrogen atom now has control of eight electrons and has a complete outer shell, while each hydrogen atom has control of two electrons and also has a complete outer shell. 3 The methane molecule ● A carbon atom has four electrons in its outer shell and needs another four electrons to complete the shell. In methane, four hydrogen atoms each donate one electron to form four C-H bonds. The carbon atom now has control of eight electrons and has a complete outer shell, while each hydrogen atom has control of two electrons and also has a complete mation Ltd.

outer shell. or Visual Inf

carbon atom 4 hydrogen amolecule (CH4) atoms © Diagram 44

ELEMENTS AND COMPOUNDS Chemical combination: Key words coordinate bonding ammonium ion covalent coordinate compound bonding hydronium ion 1 Ammonium ion covalent bond lone pair H H + Coordinate bonding ● Coordinate bonding is a particular • form of covalent bonding in which one N • N atom provides both electrons that the two atoms share. H H+ H H 1 Ammonium ion H H ● There is a non-bonding or lone pair of electrons on the nitrogen atom of an ammonia molecule. Nitrogen uses this lone pair to form a coordinate bond with a hydrogen ion, forming the 2 Hydronium ion + ammonium ion, NH4 . H H + 2 Hydronium ion + ● The hydronium ion, H3O , forms in a • similar way. O • O 3 Aluminum chloride H H+ H H ● The Al3+ ion is very small and carries a high charge. It attracts electrons so strongly that aluminum chloride is a

covalent compound. It exists as Al2Cl6 molecules in which two AlCl3 molecules are linked by coordinate bonds formed by the donation of lone 3 Aluminum chloride pairs of electrons from two chlorine

atoms. Cl

• • Cl Cl 4 Ionic compounds with covalent character Al Al ● The ions in a sodium chloride lattice • are perfectly spherical. Thus the bonds Cl Cl • in this compound are said to be Cl perfectly ionic. ● But in an ionic compound consisting of a small, highly charged positive ion and a large negative ion such as 4 Ionic compounds with covalent character lithium iodide, the positive ion attracts electron charge away from the negative ion. The result is that the negative ion becomes distorted, and electron density becomes concentrated between the ions, + – + – mation Ltd. Na Cl Li I or creating a bond similar to a covalent bond. Compounds like lithium iodide

Visual Inf are said to be ionic with covalent character. © Diagram 45

Mixtures and solutions CHANGES IN MATTER

Key words Producing a solution emulsion suspension ionic compound mixture soluble solution

1 Solutions ● A solution is a homogeneous mixture of substances. Particles in solutions are very small and cannot be seen. The particles may be atoms, ions, or molecules, and their diameters are water salt clear liquid typically less than 5 nm. Salt dissolves in water to form a clear colorless solution. ● Many, but not, all ionic compounds are soluble in water. ● A small proportion of organic Producing a suspension compounds are soluble in water. However, organic compounds are generally more soluble in organic solvents such as hexane and ethanol. 2 Suspensions ● A suspension is a heterogeneous mixture of two components. The particles will settle out over a period of time. Suspended particles have diameters that are typically 1,000 nm or more. ● When flour is mixed with water, it water flour cloudy mixture with solid forms a white suspension. Tiny particles in the liquid particles of flour are suspended in the water. The flour particles can be filtered off from the suspension. 3 Emulsions Producing an emulsion ● An emulsion is a colloidal dispersion of small droplets of one liquid in another (See page 46). ● When oil and water are mixed, they form an emulsion. Oil is less dense than water and forms the upper layer. ● Tiny oil droplets are suspended in the water. After a while, the oil droplets join together, and two layers are formed. ● The mixture of oil and water can be separated using a separating funnel. mation Ltd.

water oil cloudy mixture liquids separate or forming an emulsion when left when shaken to stand Visual Inf © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● ● ● ● ● ● ● Colloids foam filtration emulsion colloid aerosol Key words suspensions between thosein fine network in a liquid to form ajelly.fine networkinaliquidtoform asa arranged Gels aresolidparticles suspended inaliquid. are whensolidparticles Sols form liquid. a of whensmallparticles Emulsions form in aliquidorsolid. Foams whenagasissuspended form another gas. suspendedinairor liquid particles Aerosols areextremelysmallsolidor emulsions The maintypesare: original phasesoftheirconstituents. Colloids areclassifiedaccordingtothe ter areanalogoustothe These terms medium anddispersedsubstance. A and centrifugation. techniqueslike by ordinary separated fromthedispersionmedium inacolloidcannotbe The particles standing. diameter anddonotsettleon approximately 500nmorlessin inacolloidare The particles will settleoveraperiodoftime. inasuspension more. Theparticles diameter oftypically1,000nmor inasuspensionhave The particles par A colloid consistsofadispersing colloid ms soluteandsolvent. ticles whosesizeisintermediate liquid aresuspendedinanother CHANGES INMATTER sa is , sols . substance madeof , 46 and solutions suspension solution sol gel aerosols gels . and filtration , foams , Colloids 2 1 3 1 1 1 solid sol gel solid foam sol emulsion foam aerosol aerosol Colloid type Colloid type Colloid type In Air In solids In liquids dispersing medium 2 dispersing medium 2 dispersing medium 2 Phase of Phase of Phase of solid solid solid liquid liquid liquid gas gas cork dispersed substance 3 dispersed substance 3 dispersed substance 3 Phase of Phase of Phase of solid liquid gas solid liquid gas solid liquid paint polystyrene aerosol alloys agar, geletine, jelly cork, polyurethane milk of magnesia, paint milk, salad dressing froth, whippedcream dust, smoke clouds, fog, insecticide spray Examples Examples Examples 47

Simple and fractional CHANGES IN MATTER distillation Key words boiling point distillation Simple distillation of sea water fractional distillation boiling point (°C) mixture

c f water 100 salt 1,420 1 Simple distillation ● Distillation is a process in which a mixture of materials is heated to separate the components. ● Simple distillation is used when the boiling points of the components are widely separated. ● In the diagram, salt water is placed in a a round-bottom flask. Water boils at 100°C and becomes water vapor. ● A condenser consists of an inner tube d e surrounded by a jacket of cold water. This jacket ensures that the inner tube remains cool. g b ● The vapor passes into the condenser, where it is cooled and changes back into liquid. ● The water runs out of the condenser and is collected in a second flask. ● The salt remains in the round- Fractional distillation of ethanol bottomed flask. c boiling point (°C) 2 Fractional distillation water 100 ● Fractional distillation is used to separate components whose boiling f ethanol 78 points are similar. ● Ethanol boils at 78°C and turns to vapor. Because the boiling point of water is only 100°C, a significant 78°C amount of water also becomes vapor as a result of evaporation. 79°C ● The fractionating column contains 80°C glass beads, which provide a large surface area for vapor to condense and i the resulting liquid to subsequently boil. d e ● As the vapor mixture moves up the fractionating column, it condenses and j then boils again to become vapor. h Each time, the proportion of ethanol a sea water in the mixture increases. b heat source c thermometer

d condenser with cold water mation Ltd. e cold water in or f cold water out g distillate of pure water b h solution of alcohol and water Visual Inf i fractionating column of glass beads j distillate of ethanol © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● solution 2 ● ● ● two solids 1 residue mixture insoluble immiscible filtrate Key words iodine respectively. water—evaporate, leavingsaltand solvents the evaporating basinsandleft, intoseparate When thelayersarerun thelower layer.than waterandforms Carbon tetrachlorideismoredense two layersinaseparatingfunnel. immiscible, Water andcarbontetrachlorideare tetrachloride. in thewaterandiodinecarbon carbon tetrachloride,thesaltdissolves shaken inamixtureofwater and When amixtureofsaltandiodineis tetrachloride. far moresolubleincarbon Iodine isslightlysolubleinwaterbut carbon tetrachloride. Salt dissolvesinwaterbutnot remains. ethanol evaporates,andsolidsugar opentotheair,If thefiltrateisleft the solution, passesthroughthefilter. in thefilter undissolved saltremainsasthe When themixtureisfiltered, Sugar is insoluble sugar dissolveswhilethesaltdoesnot. and saltismixedwithethanol,the Separating amixtureof Separating twosolutesin CHANGES INMATTER —carbon tetrachlorideand soluble . When amixture . The they donotmix,andfor 48 in ethanol,whilesaltis filtrate, solvent soluble sugar of sugar residue m Separating solutions d c b a 2 1 Brown solution of purple solution of iodineincarbontetrachloride salt solution inwater sugar solution salt leftonfilter paper Separating amixture of two solids salt andiodine Separating two solutes insolution Salt andsugar mixture mixture — sugar dissolves Ethanol isaddedto d c but not salt Carbon tetrachloride is added Each of thesolvents are evaporated a off to obtain the two solutes The solution is filtered The two immiscible solutions d c are separated usinga separating funnel The ethanol evaporates leaving solid sugar b 49

Paper chromatography CHANGES IN MATTER

Key words 1 Paper chromatography chromatography solvent support Rf value mixture solute solution

chromatography paper 1 Paper chromatography ● Chromatography is a technique for separating and identifying mixtures of solutes in solutions. ● In paper chromatography, absorbent paper is suspended on a support so that only the bottom rests in the solvent front solvent. ● A base line is drawn in pencil above the level of the solvent. (If ink were used, the dyes in the ink would separate during the process and mix with the sample.) sample ● A concentrated solution of the sample mixture is made by dissolving as much pencil line as possible in a very small volume of solvent. solvent ● A small amount of the concentrated solution is spotted onto the base line. The chromatography paper is suspended over the solvent. ● 2 R value The solvent rises up the f chromatography paper. solvent front

2 Rf value ● The Rf value is the ratio of the distance moved by a substance in a chromatographic separation to the distance moved by the solvent. The R = 0.7 greater the attraction between a f substance and the solvent molecules,

the greater the Rf value. ● The molecules of each substance in a 10cm mixture are attracted both to the chromatography paper and to the solvent molecules. R = 0.4 f ● The greater the attraction between a 7cm substance and the solvent molecules, the quicker it will be carried up the chromatography paper. Dyes that are 4cm very soluble in the solvent are carried up to the top of the paper, while those that are less soluble remain lower

Rf = 0.1 mation Ltd.

down. or 1cm base line ● The Rf value is independent of the

height of the solvent front but is Visual Inf dependent on the solvent used. © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● 2 ● ● ● ● ● chromatography 1 gas-liquid chromatography alkane Key words stationar ions. substancebymeansof analyzingits a solid, suchascharcoalorsilica. identified. fromwhichitcanbe spectrum Each compoundgivesacharacteristic finally recorded. detected electrically, amplified,and The intensityoftheionbeamis the ions,greaterdeflection. path byamagneticfield.Thelighter field anddeflectedalongacircular The ionsareacceleratedbyanelectric ions. aseriesofpositive electrons andforms chamber, whereitisbombardedby The samplepassesintotheionization to identif Mass spectrometry spectrometer. detector ordirectlyintoamass The separatedcompoundspasstoa phase. to thestationary different ratesduetotheirattraction sample passthroughthecolumnat gas.Variouscarrier compoundsinthe car chamber whereitvaporizesandis A helium, orargon. gas—usually nitrogen,hydrogen, The mobilephaseconsistsofacar In stationar phase betweena partitioned In alkane point liquid,suchasalong-chain column, consistsofahigh-boiling of thesample. The mobilephaseisthecomponents retards thecomponentsofsample. Gas-liquid Mass spectrometry chromatography sample mixtureisinjectedintothe gas-liquid chromatography chromatography, substancesare ried throughthecolumnby CHANGES INMATTER and amobilephase ted byaporousinert , suppor y phase,packed intothe y phaseisthesubstancethat y thechemicalconstitutionof 50 is atechniqueused stationary phase mobile phase mass spectrometry stationary . The , the rier mass spectrometry chromatography and Gas-liquid 2 gas carrier 1 Gas-liquid chromatography Mass spectrometry amplifier recorder reservoir sample inlet column oven electron gun particles particles heavier lighter sample injection of ionisation chamber flow meter vacuum plates negatively charged field magnetic variable recorder detector 51

The pH scale CHANGES IN MATTER

Key words 1 pH scale acidity alkalinity pH [H+]/mole dm–3 pH meter

1 10–1 10–2 10–3 10–4 10–5 10–6 10–7 10–8 10–9 10–10 10–11 10–12 10–14 10–14

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 pH scale pH ● pH is a measure of the acidity or alkalinity of a solution. The term pH was originally introduced by the Danish biochemist Søren Sørensen in 1909 while working on methods of improving the quality control of beer. Increasing acidity Increasing alkalinity The letters pH stand for “potential of hydrogen.” Neutral ● Acidic solutions always have a pH of less than 7, and alkaline solutions always have a pH of more than 7. The Lower pH/sronger acid Higher pH/sronger alkali lower the pH value, the more acidic the solution; conversely, the higher the pH value, the more alkaline the solution. ● The pH of a solution is the logarithm to base 10 of the reciprocal of the numerical value of the hydrogen ion concentration: pH = lg(1/[H+]0 = -lg [H+] 2 Schematic of a pH meter ● The pH of a neutral solution can be calculated directly from the ionic b product (Kw) of water: + - -14 2 -6 Kw = [H ][OH ] = 10 mol dm For a neutral solution: [H+] = [OH-] = 10-7 mol dm-3 therefore the pH of a neutral solution = 7. ● The pH scale is logarithmic, so c a hydrogen ion concentration increases or decreases by a power of 10 for each step down or up the scale. 2 pH meter d ● A pH meter is an electrochemical cell consisting of an electrode, such as a h e glass electrode, which is sensitive to g hydrogen ion concentration, and a f reference electrode. ● The emf (electromotive force) of the cell can be measured using a high- resistance voltmeter. A pH meter is a mation Ltd.

high-resistance voltmeter calibrated or a platinum wire e capillary opening with porous plug with the pH scale. b sensitive voltmeter f solution of unknown pH c silver wire coated with silver g Thin glass membrane through which H+ ions can pass Visual Inf chloride (AgCl) h solution of fixed acid pH d saturated potassium chloride (KCl) © Diagram © Diagram Visual Information Ltd. ● ● 4 ● 3 ● ● 2 ● 1 end point alkali acid-base acid Key words lef equilibrium anions. Underacidicconditions,the dissociates inwater, pink forming is acolorless,weakacidthat enough forthepinktobeseen. concentration ofanionsishigh equilibrium istotheright,and visible. Underalkalineconditions,the anions istoolowforthecolortobe and alkaliistobe used. combination of strongandweakacid in atitrationdepends onwhat The suitabilityofanindicatorfor use equivalent amountsofacidand alkali. titration, thepointatwhichthere are time totheequivalencepointof the color change,occursatadifferent indicator undergoesthemaximum titration, This meansthattheendpoint when thepHofasolutionisexactly7. Most indicatorsdonotchangecolor alkaline asolutionis. colors thatindicatehowacidicor universal indicator a base onlyinthebroadestterms, show whetherasubstanceisanacidor phenolphthalein, whichisableto In contrasttoanindicatorsuchas Phenolphthalein issuchanindicator the solution. reaction and,therefore,thecolorof position oftheequilibrium changeinpHcausesathe A that isadifferentcolorthantheacid. acids thatdisassociatetogiveanion Acid-base indicatorsareusuallyweak solution isanacidoralkali. alkalis that aredifferentcolorsin Acid-base indicators Common indicators Universal indicator Changing equilibrium indicator pH rangeofindicators t, andtheconcentrationof CHANGES INMATTER so they“indicate”whethera the pointatwhich of thereactionisto 52 universal titration equilibrium has arangeof are substances indicator acids of the and . It 3 1 change color 4 Indicators 0234567891011 hnlhhli ools pink yellow blue colorless phenolphthalein red red methyl orange litmus phenol red phenolphthalein methyl red methyl orange bromothymol blue bromocresol green 2 Table of common indicators Universal indicator Table of pHrange over whichacid–base indicators Changing equilibrium(phenolphthalein) OH Indicator 1 niao oo nai Colorinalkali Colorinacid Indicator e rneylo re blue green yellow orange red colorless O C C (acid) O yellow colorless yellow red yellow yellow cdAlkali Acid + H OH 2 O Color Color pH red pink red yellow blue blue OH (base) C C pink O O – 6.8–8.4 8.2–10.0 4.8–6.0 3.2–4.4 6.0–7.6 3.8–5.4 change occurs pH range over which color 21 14 13 12 purple + H OH 2 O + 53

Titration of strong acids CHANGES IN MATTER

1 Titration of strong acid against strong alkali Key words acid titration 3 (pH changes during the titration of 50 cm of 0.1M HCl alkali with 0.1M NaOH) base end point 12 pH

1 Titration of strong acid 10 against strong alkali ● phenolphthalein At the end point of strong acid–strong base alkali titration, the pH changes 8 by 5 or 6 pH units when only 1 drop of acid or alkali is added.

r bromothymol blue e ● Methyl orange, bromothymol blue, b

m and phenolphthalein are all suitable

u 6 n indicators for this titration because H p they all change color within a very 4 small change in volume of sodium methyl orange hydroxide solution. 2 Titration of strong acid 2 against weak alkali ● At the end point of a strong acid–weak alkali titration, the pH change for the 0 0 1020 30 40 50 60 70 80 90 100 addition of one drop of acid or alkali is Volume of 0.1 M NaOH added (cm3) significant. However, the pH at equivalence (when there are equivalent amounts of acid and alkali) is less than 7. A suitable indicator 2 Titration of strong acid against weak alkali should change color below or around (pH changes during the titration of 50 cm3 of 0.1 M HCl pH 7. Thus both methyl orange and with 0.1 M NH ) bromothymol blue would be suitable 3 indicators because they change color between pH 3.2 and 7.6. Within this 12 range, the pH of the titration mixture changes significantly for a very small change in volume of sodium 10 hydroxide solution. phenolphthalein ● Phenolphthalein would not be a good choice of indicator because it changes 8 color between pH 8.2 and 10.0. In order to change the pH of the titration r

e bromothymol blue mixture over this pH range, a b

m significant volume of sodium

u 6 n hydroxide solution must be added. H

p The result would be an overestimate of the volume of sodium hydroxide 4 methyl orange solution needed to neutralize the acid.

2 mation Ltd. or Visual Inf 0 0 1020 30 40 50 60 70 80 90 100 Volume of 0.1 M NH added (cm3)

3 © Diagram © Diagram Visual Information Ltd. ● ● against weakalkali 2 ● ● against strongalkali 1 pH equivalence point end point alkali acid Key words type oftitration. There isnosuitableindicatorforthis the equivalencepointaccurately. done, apHmeterisnecessar with weakalkali,butifitmustbe It isnotusualtotitrateweakacids accurate results. phenolphthalein wouldnotgive orange, bromothymolblue,or of acidoralkali.Theusemethyl change withtheadditionofonedrop equivalence pointtogiveacolor The pHchangestooslowlyaroundthe neutralize theacid. sodium hydroxidesolutionneededto be anunderestimateofthevolume titration isreached.Theresultwould before theequivalencepoint between pH3.2and7.6,whichis choices becausetheychangecolor methyl orangewouldnotbegood Conversely, bromothymolblueand hydroxide solution. change involumeofsodium small changes significantlyforavery range, thepHoftitrationmixture between pH8.2and10.0.Within this choice becauseitchangescolor phenolphthalein wouldbeagood should changecolorabovepH7.Thus is greaterthan7.Asuitableindicator equivalent amountsofacidandalkali) the pHatequivalence(whenthereare acid oralkaliissignificant.However change fortheadditionofonedrop acid At the Titration ofweakacid Titration ofweakacid –strong CHANGES INMATTER end point alkali titration 54 of aweak titration the , y of the to find pH , Titration ofweakacids 2 1 pH pH Titration ofweakacidagainststrongalkali Titration ofweakacidagainstalkali 14 14 0 7 0 7 methyl orange bromothymol blue phenolphthalein methyl orange bromothymol blue phenolphthalein Volume of base Volume of base 55 pH and soil CHANGES IN MATTER

1 Soil classification Key words

pH Description pH

< 5.5 strongly acid

5.5 – 5.9 medium acid

6.0 – 6.4 slightly acid 6.4 – 6.9 very slightly acid 1 Soil classification 7.0 neutral ● Soil can be classified according to its 7.1 – 7.5 very slightly alkaline pH. ● Soils naturally tend to become more 7.6 – 8.0 slightly alkaline acidic due to organic acids being 8.1 – 8.5 medium alkaline released into the soil as a result of the decay of organic material. > 8.5 strongly alkaline ● The acidity of soil can be reduced by 2 pH range of common fruit and vegetables spreading slaked lime (calcium hydroxide) or lime (calcium Fruit or vegetable Soil pH range carbonate). cabbage 6.0 – 7.5 2 pH range of common cauliflower 6.5 – 7.5 fruits and vegetables celery 6.5 – 7.5 ● Most plants grow best in soil that is cucumber 5.5 – 7.0 slightly acidic, with a pH value between 6.3 and 7.2. Plants will grow potato 5.0 – 6.0 outside this range but not as well. This peas 6.0 – 7.5 has serious implications for food crops. strawberry 5.0 – 6.0 ● The soil pH is an important tomato 5.5 – 7.0 consideration in preparing soil to grow crops. 3 Elements needed by plants 3 Elements needed by plants 10.0 ● Plants need a number of major and Easy to minor elements in order to grow well, absorb 9.0 and they obtain these from the soil. Difficult to The minerals dissolve in soil water and absorb are absorbed into the plant through 8.0 the roots. ● The pH of the soil determines how easily minerals containing these pH 7.0 elements can be absorbed. At soil pH values between 6.0 and 7.0, all major elements and minor elements can be 6.0 absorbed, although some are absorbed more easily than others. In very acidic or very alkaline soils, relatively few 5.0 plants prosper because they cannot absorb all of the minerals needed for healthy growth. 4.0 mation Ltd. or n s r n e n r c m m m m e u u o s o e n r u u u f r r i u g i i i l e p I Z o o s c s u n o p n r h l e s e S a B o t a d g Visual Inf i p a n C s t b N C g n o o y a a l h P M o P M Minor elements Minor elements M © Diagram © Diagram Visual Information Ltd. ● ● 3 ● ● 2 ● ● 1 ● ● The watercycle convection atmosphere Key words of Ear precipitation, which falls to Earth. precipitation, whichfallstoEarth. eventually depositedintheoceans. initand dissolved solidsarecarried sea, thuscompletingthecycle.Any rivers. Finally, thewaterflowsoutto to the this waterisultimatelyreturned industrial anddomesticuse.Muchof Water isremovedfromriversforboth it. through theground,solidsdissolvein streams andrivers.Asthewaterflows through soilsbeforegatheringin The freshwaterflowsoverrocksand which makes itslightlyacidic. dissolvedgases, contains Rainwater upon are carried When cloudsreachlandmasses,they which car clouds. Thesearedispersedbywinds, where iteventuallycondensestoform Water vaporrisesintothe wheretheseasarewar of Earth rate ofevaporationisgreaterinareas all dissolvedsubstancesbehind.The oftheoceans,leaving from thesurface Heat energycauseswatertoevaporate the cycle. The Sunprovidestheenergydriving cycle. cycle calledthehydrologicorwater waterisalwaysmovingina Earth’s vapor condenses,for decreases, andeventuallythewater As theyrise,thetemperature Evaporation Deposition Transportation current CHANGES INMATTER th. ry themtothecolderregions ry 56 convection cur ming atmosphere mer. rents , . The watercycle 1 2 3 Evaporation Deposition Transportation evaporation evaporation evaporation transportation condensation ufc uofgroundwater flow surface runoff precipitation 57

Treatment of water and CHANGES IN MATTER sewage Key words methane oxidizing agent 1 water treatment sewage

a b h

1 Water treatment ● Particles are removed from water by passing it through a series of sand filter beds and sedimentation tanks. The filter beds also contain bacteria, which break down and destroy microorganisms in the water. ● Chlorine is a powerful oxidizing agent that is used to kill any remaining microorganisms in the water before is stored ready for distribution. Storage tanks are covered to prevent the entry of foreign bodies. 2 Sewage treatment d e c f g b i ● Raw sewage cannot be released into rivers because of the threat to health and the effects on the environment. 2 Sewage treatment The waste materials it contains must first be broken down by the action of decomposing bacteria. j a b c l c n ● Solids are removed from the sewage by a series of screens and settling tanks. The remaining liquid passes into a digester, where bacteria break down the waste products. Streams of air are blown into the tank in order to provide the bacteria with the oxygen needed to survive and to keep the mixture circulating. ● After settling, the clean water is allowed to pass into the river, while o the sludge undergoes further digestion during which methane is released. The digested sludge contains nitrogenous compounds and is often used as a fertilizer.

k m p

a screen i to homes and factories b pump j sewage in mation Ltd.

c sedimentation tank k settling tank or d water in l digester aeration tank e coarse sand filter m sludge collected f fine sand filter n clean water to river Visual Inf g chlorine added o methane out h covered storage tank p digested sludge out © Diagram © Diagram Visual Information Ltd. ● molecule 3 ● ● 2 ● A 1 lone pair hydrogen covalent bond Key words ␦ notation; oxygenis slightly positive.Thisisshownusing negative andthehydrogenatom leaves theoxygenatomslightly electrons arenegativelycharged,this closer totheoxygenatom.Since is thattheelectronsinbondreside the oxygen–hydrogen stronger attractionfortheelectronsin hydrogen and,therefore,hasa Oxygen ismoreelectronegativethan oxygen–hydrogen bondsto104.5°. reduces theanglebetween and thebondingpairsofelectrons of more stronglythanthebondingpairs pairs ofelectronsrepeleachother Thenon-bonding shape isdistorted. thetetrahedral tetrahedron. However, ofa directed towardthecorners These fourpairsofelectronsare (sometimes calledlonepairs). two pairsofnon-bondingelectrons (sometimes calledsharedpairs)and has The oxygenatominawatermolecule hydrogen compound Water isessentiallya The polarnatureofthe + The watermolecule compound . electrons. Repulsionbetweenthese two pairsofbondingelectrons covalent compound CHANGES INMATTER and oneatomof formed bytwoatomsof formed 58 ␦ oxygen - covalent and hydrogenis bond. oxygen The result . ␦ The watermolecule 1 3 2 H A The polarnature of themolecule The water molecule H covalent compound electron one outer-shell tm rsn Full shellsof awater molecule Atoms present Water molecule shared pairs nearer theoxygen O O H H six outer-shell electrons electron one outer-shell H δ + Non-bonding pairs (lone pairs) O O δ – H δ + H O H Bonding pairs 104.5° O H H 59

Water as a solvent of CHANGES IN MATTER ionic salts Key words anion hydration body-centered ionic crystal 1 Ionic lattices cubic lattice cation face-centered cubic

1 Ionic lattices ● The ions in an ionic crystal are arranged in a lattice. Each ion is surrounded by a number of oppositely charged ions. The lattice structure is determined by: - the ratio of the number of positively charged ions (cations) to negatively charged ions (anions) - the ratio of the radii of the ions (rcation / ranion) – + Cl ion Cs ion ● The radius ratio in sodium chloride is Na+ ion Cl– ion 0.57. The ions are arranged in a face- centered cubic structure in which each sodium ion is surrounded by six 2 The effect of water on an ionic lattice chloride ions, and each chloride ion is surrounded by six sodium ions. H a H c ● The radius ratio of cesium chloride is H 0.94 (due to the larger cesium ion). O O HH O HHO The ions are arranged in a body- H H centered cubic structure in which O H O HH H H each cesium ion is surrounded by H O O eight chloride ions, and each chloride H ion is surrounded by eight cesium H H H ions. O O H H 2 The effect of water on an O ionic lattice b H ● When an ionic compound is placed in Ionic lattice put into water The ions attract the water molecules water, the water molecules collide with the lattice. If the water molecules H H H collide with sufficient energy to O overcome the forces of attraction O H O between the oppositely charged ions, O H hydration occurs, and the compound HH will dissolve, forming a solution. H H O

H H H O mation Ltd. or

The lattice starts to split up Visual Inf a lattice c charged ends of molecules attracted b water molecules to ions of opposite charge © Diagram © Diagram Visual Information Ltd. ● ● chloride 3 ● ● ● solution 2 ● ● 1 ● Ionic solutions ionic compound ion cation bond anion Key words an ionic more stablewhenbondedtogether in The silverionsandchloride are Ag precipitate. awhite insoluble silverchlorideforms sodium chloridesolutionaremixed, When silvernitratesolutionand solutions. when solidsareobtainedfromtheir water aresostrongthattheyremain The bondsbetweenthemetalionsand coordinatebonds. form the watermoleculesaredonatedto Non-bonding pairsofelectronsfrom electric chargeonthewatermolecule. outer shellandcanfillthiswiththe T with water T atoms. are stabilizedbythepositivehydrogen atoms, andnegativelycharged stabilized bythenegativeoxygen positively charged stabilize the W positively charged. the hydrogenatomsareslightly atom isslightlynegativelychargedand bonds electrons intheoxygen–hydrogen Due totheunevensharingof dissolved inwater. Ionic solutionsare s Stabilizing freeions urrounded bywatermolecules. urrounded ransition metal ransition metalshaveanincomplete Production ofsilver Transition metalsin ater molecules surround and ater moleculessurround + (aq) +Cl CHANGES INMATTER of awatermolecule,theoxygen lattice . ions - (aq) than existingapart 60 in thecompound: ions form ➞ cations ionic compounds transition metals lattice AgCl(s) are complexes anions Ionic solutions solution Silver nitrate solution and sodium chloride H H H added to silver nitrate solution 3 2 1 H H Stabilizing freeions Production of silver chloridewhenametal chlorideis Transition metalsinsolution H O HH H O O H H O O HH H Ag Na O H O H H O H + O + O H O O O H H H H H H O O H H H oxygen atom negatively charged - H H H O H O H H H H O H H OO OO H H HH Cl O O H H H H HH O – H HH H H NO H O H O O H HH H M O O H – 3 O O H O H H H H H H O leave solid silver chloride aqueous silver andchlorideionsto molecules have been forced away from After reaction, clusters of water HH O H H H O O HH Na O H O + O H H H H O H H hydrogen atom positively charged + H O O H H H H Ag Cl Cl H H O – – + H O H H O Ag Ag HH Cl NO HH – O + + H H O – 3 Ag Cl Cl O H – – + 61

Solubility CHANGES IN MATTER

1 Table of solubility of ionic compounds Key words ionic compound Soluble Insoluble insoluble soluble all salts of ammonium, potassium, and sodium

all nitrates 1 Solubility of ionic compounds ● All ionic compounds are soluble in most bromides, chlorides, and iodides lead and silver bromides, chlorides, and iodides water to some extent. However the solubility of some is so low that they are best regarded as insoluble. most sulphates (calcium sulfate is barium and lead sulfate Solubility generally follows the slightly soluble) following rules. ● All ammonium, potassium, and ammonium, potassium, and sodium most other carbonates sodium salts are soluble. carbonate ● All nitrates are soluble. ● With the exception of lead and sliver bromides, chlorides, and iodides, ammonium, potassium, and sodium most other hydroxides hydroxides (calcium hydroxide is slightly bromides, chlorides, and iodides are soluble) soluble. ● Most sulfates are soluble, with the exception of barium and lead sulfate. 2 Table of the most abundant compounds in seawater ● Most carbonates are insoluble, with the exception of ammonium, Name of compound Formula of compound Percentage of solids potassium, and sodium carbonate. in seawater ● Most hydroxides are insoluble, with sodium chloride NaCl 78 the exception of ammonium, potassium, and sodium hydroxides. magnesium chloride MgCl2 9 ● Calcium hydroxide is only slightly soluble. magnesium sulphate MgSO4 7

calcium sulphate CaSO 4 2 Most abundant 4 compounds in seawater potassium chloride KCl 2 ● Seawater is a solution of many different salts. The main salt present in calcium carbonate CaCO less than 1 3 seawater is sodium chloride. ● magnesium bromide MgBr2 less than 1 The concentration of solids in seawater depends on the location. The saltiest water occurs in the Red Sea, where there is 40 g of dissolved solids per 1,000 g of water. The North Atlantic is the saltiest of the major oceans, with an average of 37.9 g of dissolved solids per 1,000 g of water. The least salty waters are found in polar seas and the Baltic Sea, which contains only 5–15 g of dissolved sodium magnesium solids per 1,000g of water.

chloride bromide mation Ltd. 78 % <1 % or

magnesium magnesium calcium potassium calcium Visual Inf chloride sulfate sulfate chloride carbonate 9 % 7 % 4 % 2 % <1 % © Diagram © Diagram Visual Information Ltd. ● ● ● ● Expressing solubility solubility curve Key words of water)and100° varies between0°C(thefreezingpoint shows howthesolubilityofasalt of nitrate). or increases gradually(potassiumsulfate) while thesolubilityofotherseither nearly constant(sodiumchloride), the solubilityofsomesaltsremains C, Over thetemperaturerange0–100° are generallynotstraightlines. temperature range.Solubilitycur of thecompoundoverwhole plotted usingdataaboutthesolubility ofacompoundis The solubilitycurve A temperature forwhichitisgiven. solubility, tostatethe itisnecessary with temperature,sowhenquoting increases) compound varies(normally / g expressedin Solubility isnormally solubility curve water). increases ver 100 gofwater. Thesolubilityofa CHANGES INMATTER y 62 rapidly (potassium C (theboilingpoint is agraphthat ves Solubility curves Mass of crystals that dissolve in 100g of water (g) 100 120 110 80 40 60 90 20 50 30 70 10 0 02 04 06 08 90 80 70 60 50 40 30 20 10 0 c b a potassium sulfate sodium chloride potassium nitrate Temperature (°C) a c b 100 63

Solubility of copper(II) CHANGES IN MATTER sulfate Key words saturated 1 Table of solubility of copper(II) sulfate at solute solution different temperatures solubility curve

Temperature °C Solubility Temperature °C Solubility g/100g water g/100g water 1 Solubility of copper(II) 0 14.3 60 40.0 sulfate at different 10 17.4 70 47.1 temperatures ● When no more solid will dissolve in a 20 20.7 80 55.0 solution at a given temperature, the 30 24.3 90 64.8 solution is said to be saturated. ● Normally when a solution is cooled 40 28.5 100 75.4 below the saturation temperature for the quantity of solute present, some 50 34.0 solute crystallizes out. Under certain conditions a solution may be cooled 2 Solubility curve for copper(II) sulfate below this temperature without crystallization occurring. Such a solution is said to be supersaturated. ● A solubility curve is plotted by finding 70 the amount of solid needed to make a saturated solution at a number of + different temperatures over the range 0–100°C. 60 2 Solubility curve for + copper(II) sulfate ● The solubility of copper(II) sulfate at 76°C is found by drawing a vertical line 50 from 76°C to the solubility curve and r

e + t then a horizontal line to the solubility a

w axis. The value is 52 g of copper(II) g

0 sulfate per 100 g of water. 0 1 ● / 40 + The temperature at which the g

y solubility of copper(II) sulfate is t i l i exactly 36 g per 100 g of water is b u l +

o found by drawing a horizontal line S from 36 g / 100 g water to the 30 + solubility curve and then a vertical line to the temperature axis. The + temperature is 54°C. ● The solubility of copper(II) sulfate at 20 + 90°C is 64.8 g / 100 g water and at 20°C + is 20.7 g / 100 g water. If 100 g of saturated copper(II) sulfate solution was allowed to cool from 90°C to 20°C 10 the mass of copper(II) sulfate crystals formed would be 64.8 – 20.7 = 44.1 g. ● mation Ltd. The size of crystals formed is related or to how quickly the solution is cooled.

If cooling is rapid many small crystals Visual Inf 0 0 10 20 30 40 50 60 70 80 90 100 are formed but if cooling is slow a smaller number of large crystals are Temperature (°C) formed. © Diagram © Diagram Visual Information Ltd. ● ● 2 ● ● ● Kipps apparatus 1 hydrogen hydrochloric acid dry gas anhydrous Key words because itislessdensethanair. (downward displacementofair) is collectedbyupwarddeliver anhydrous Hydrogen isdriedbypassingthrough all watervaporhasbeenreduced. A of thegas. obtaineddirectlyfromacylinder often laboratory, hydrogenis In amodern reaction stops. andthe of themiddlecompartment, hydrochloric acidbackdownandout sufficient toforcethedilute increases. Eventuallythepressureis gradually the middlecompartment time, andthepressureofgasin continues tobeproducedforashort If thetapisclosed,hydrogen Zn(s) +2HCl(aq)➞ hydrogen: hydrochloric acidtoproduce compar granulated zincinthemiddle the levelrisesuntilitreactswith and floods thebottomcompartment is opened,dilute using aKippsapparatus.Whenthetap Traditionally, Obtaining hydrogenusing Collecting dryhydrogen dry gas dry PATTERNS—NON-METALS tment. Zincreactswithdilute is anaturalgasfromwhich calcium chloride.Thegas hydrogen 64 hydrochloric acid ZnCl is 2 generated (aq) +H y 2 (g) Hydrogen: preparation 2 1 Obtaining hydrogen usingKipps apparatus Collecting dryhydrogen b a b a c b a c b a hydrogen gas dilute hydrochloric acid granulated zinc gas chloride anhydrous calcium Kipps apparatus damp hydrogen from c c 65

Hydrogen: comparative PATTERNS—NON-METALS density Key words carbon dioxide diffusion 1 Gaseous diffusion of hydrogen in air Graham’s law hydrogen 1A 1B

a a 1 Gaseous diffusion of b b hydrogen ● Gases are able to pass into and out of c c a porous vessel. ● Hydrogen is less dense than air, so it is contained in an inverted beaker (1A). ● Hydrogen diffuses into the porous vessel more quickly than air diffuses out of it. ● The gas pressure inside the porous vessel increases and becomes greater than atmospheric pressure (1B). Liquid is forced up the right side of the manometer (an instrument used d d to measure the pressure of a fluid). 2 Gaseous diffusion of carbon dioxide ● Carbon dioxide is more dense than air, so it is contained in an upright beaker (2A). ● Carbon dioxide diffuses into the porous vessel more slowly than air 2 Gaseous diffusion of carbon dioxide in air diffuses out of it. 2A 2B ● The gas pressure inside the porous vessel decreases and becomes less than atmospheric pressure. Liquid is forced up the left side of the manometer (2B). Comparative density ● Graham’s law of diffusion states that b b the rate at which a gas diffuses (r) is proportional to the square root of 1 c c over its density (d): r ϰ͌1/d ● The density of hydrogen is lower that air. Therefore, it diffuses more quickly. ● The density of carbon dioxide is e e higher that air. Therefore it diffuses more slowly.

d d mation Ltd. or Visual Inf a hydrogen c porous vessel e carbon dioxide b air d manometer © Diagram © Diagram Visual Information Ltd. ● ● 4 ● ● 3 ● ● ● ● 2 ● ● ● ● 1 electrolysis cathode calcium anode anhydrous Key words needed forthereactiontostar H reaction This isanexampleofa react inbrightlight. A Pb for acetate paperblackduetothe damplead Hydrogen sulfideturns H produce Hydrogen reactswithsulfurto water. chloride paperpink,showingitis anhydrousbluecobalt The liquidturns collects inthewaterglass. sur Water vaporcondensesontheouter must betheresultofcombustion. carbonate through The hydrogengasisdriedbypassingit water. inairtoproduce Hydrogen burns 2H explodes whenignited: A 4H At 4OH At theanode: Electrolysis the (positive electrode)andhydrogenat produces oxygenatthe Hydrogen andoxygen Hydrogen andsulfur Hydrogen andair carbonate hydrogen andchlorine 2 2 mixture ofhydrogenandchlorine mixture ofhydrogenandoxygen PATTERNS—NON-METALS (g) +Cl (g) +S(l) 2+ the cathode: 2 + mation of face ofthebeaker ofcoldwaterand (g) +O (aq) +4e cathode - (aq) +H (aq) . anhydrous calcium hydrogen sulfide: ➞ Light providestheenergy 2 2 (g) so anywaterproduced (g) of O ➞ (negative electrode). 2 - lead sulfide: S(g) 2 ➞ dilute ➞ (g) +2H H ➞ 66 2 2H 2HCl(g) S 2H ➞ 2 sulfuric acid photochemical lead sulfide hydrogen sulfide (g) 2 sulfuric acid PbS(s) +2H reaction O(g) 2 photochemical anode O(l) +4e t: - + (aq) j i h g f e d c b a other gases Hydrogen: reactionwith of sulfuricacid Preparation of hydrogen andoxygen from electrolysis 1 Before light isswitched on 4 2 hydrogen burning beaker containg cold water anhydrous calcium chloride hydrogen from Kipps apparatus hydrogen/oxygen mixture loose support bunsen flame polyethelene tubing platinum electrodes polyethylene bottle containing dilute H c a h b p g Explosion of hydrogen/oxygen mixture Hydrogen andair Photocatalytic explosion of hydrogen withchlorine b 2 SO q o i 4 r q p o n m l k k j white fumes of hydrogen chloride rubber bung powerful light source chlorine andhydrogen polyethylene bottle containing mixture of filter paper soaked inlead acetate boiling sulfur dry hydrogen water collected Light isswitched on with sulfur 3 l Reaction of hydrogen d Explosion technique m e n r f 67

Hydrogen: anomalies in PATTERNS—NON-METALS ammonia and water Key words ammonia group 8 boiling point hydride 1 Anomalous boiling points of ammonia and water dipole lone pair group 5 orbital group 6

H2O 100 1 Anomalous boiling points of ammonia and water ● Atoms of the group 8 elements have a 50 full outer orbital of electrons. They exist as single atoms, and there are group 6 hydrides very weak forces of attraction between H2Te 0 them. The boiling point of these NH3 group 5 hydrides elements increases in proportion to H2Se the size of the atom. ● The boiling points of the group 5 and H S SbH3

C 2 ° –50 group 6 hydrides also increases with / t n i AsH molecular size. However, the boiling o 1 3 group 8 hydrides p point of water and ammonia are g n i

l significantly higher than might be i –100 PH3 o expected when compared to the other B Xe hydrides in their groups. This is the 2 result of strong forces of attraction, –150 called hydrogen bonding, between Kr water molecules and between ammonia molecules. –200 Ar 1 expected value for water 2 Strong bonding between water molecules 2 expected value for ammonia ● There are five electrons in the outer –250 orbital of a nitrogen atom. In Ne ammonia, three of the electrons are used in nitrogen–hydrogen bonds, –300 while the remaining two form a non- 135624 bonding or lone pair. Period number ● The nitrogen atom in ammonia is more electronegative than the hydrogen atoms. The result is that a 2 Strong bonding between water molecules pair of bonding electrons lies nearer to the nitrogen atom than the hydrogen atom in each nitrogen–hydrogen N H bond. ● This forms a dipole, a chemical H compound with an unequally + δ H distributed electric charge. The nitrogen–hydrogen bond is polarized, leaving the nitrogen slightly negative δ– H δ– (sometimes shown as ␦-) and the hydrogen slightly positive (sometimes N N H + mation Ltd. shown as ␦ ). or ● The slightly positive hydrogen atom is H

attracted to the slightly negative Visual Inf H H H δ+ nitrogen atom and the non-bonding pair of electrons on neighboring

ammonia molecules. © Diagram © Diagram Visual Information Ltd. ● 5 ● ● ● 4 ● ● ● 3 ● ● 2 ● ● 1 hydrogen hydride catalyst base alkali Key words hydrogen ions, All acidsproducesolutionscontaining hydroxide. metal hydroxideslike copper(II) precipitatesofinsoluble used toform Sodium hydroxidesolutioncanbe are Metal hydroxidesthatdissolveinwater All metal oxygen. waterand to breakthisbond,forming manganese(IV) oxide,actas A unstable peroxide Hydrogen peroxidecontainsan (hydrogen peroxide). both anoxide(water)anda Hydrogen reactswithoxygentoform oxide. reactivity series,suchascopper(II) oxides Hydrogen canbeusedtoreducethe metals andnon-metals. hydrideswith both Hydrogen forms CH (See page74): industrial manufactureofammonia hydrogen fortheHaberprocessin This reactionisusedtoprovide hydrocarbons reduced byeithercarbonor Water, ofsteam,canbe intheform Preparation The oxides Acids Reactions ofhydrogen The hydroxycompounds variety ofsubstances,including PATTERNS—NON-METALS 4 alkalis (g) +H of metalsthatarelowinthe hydroxides . 2 O(g) CO(g)+3H to give H 68 + . –O-O- peroxide oxide hydroxide hydrocarbon are hydrogen. bases. bond. peroxide catalysts 2 (g) 2B 2A 1D 1C 1B 1A hydrogen Basic reactionsof 4 3 2 1 5 B A B A D C B A it reduces compound it reduces other elements laboratory preparation electrolysis of brine from oil from coal Preparation The oxides Reactions of hydrogen Acids The hydroxy compounds C H H HNO HCl Cl aH+HlNaCl NaOH +HCl 2H 2Na +2H CuO +H O 2NaOH +CuCl 2Na +H N n+2C ZnCl Zn +2HCl 2H C C 2 7 2 2 2 + SO H 2 2 + + + O O 16 H 3 4 2H 3H 2 +7H 2 H + O 2 2 2e 2 2 2 2 – 2NaOH O 2 O 2 MnO 2 4 3B 3A 2H H metallic hydroxides are bases hydrogen peroxide water 2H Cu +H 2HCl 2H 2NH 2NaH 2OH Cu(OH) 7CO CO +H + + + 2 2 + + O O +

– 3 2 +

NO Cl + + + + SO 15H – 2

2 H 2 + H O O 3 H ↓ – 2 4 2 2 H 2 O 2– + 2 2 2NaCl 69

The gases in air PATTERNS—NON-METALS

Key words 1 Composition of air argon methane carbon dioxide ozone carbon monoxide pollutant compound sulfur dioxide element

1 Composition of air ● Air is not a chemical compound but a mixture of elements and compounds. The exact composition of air varies slightly from place to place depending on conditions. For example, the proportion of carbon dioxide in the air above a forest will be less than in the air above a city. Trees remove carbon dioxide for photosynthesis, while burning fossil fuels releases carbon dioxide. Nitrogen Carbon dioxide Argon Oxygen 2 Gases present in clean dry air ● Clean dry air is approximately 80 2 Gases present in clean dry air percent nitrogen and 20 percent oxygen. ● Argon makes up the largest portion of Gases Symbol or formula Percentage of volume the remaining 10 percent. Nitrogen N 78.08 ● Air usually contains water vapor, with the amount depending on local Oxygen O 20.95 conditions. Argon Ar 0.93 3 Gases in polluted air ● Air may contain pollutants released Carbon dioxide CO2 0.04 from a variety of sources. Neon Ne ● Sulfur dioxide and nitrogen oxides dissolve in water in the atmosphere Helium He traces and increase the acidity of rainwater. Krpton Kr ● Carbon monoxide is a poisonous gas. If it is inhaled, it bonds onto the Xenon Xe hemoglobin in red blood cells and prevents them from transporting 3 Gases that may be found in polluted air oxygen. ● Ozone is essential in the upper Gases Symbol or formula Example of source atmosphere (ozone layer), where it prevents harmful ultraviolet radiation

Ammonia NH3 Industrial processes from reaching Earth. At ground level, however, it is responsible for the Carbon monoxide CO Motor vehicle exhaust formation of smog. ● Decay of organic material, passed in wind Methane and carbon dioxide are greenhouse gases. In the upper Methane CH4 by herbivorous animals mation Ltd.

atmosphere, they prevent heat or Nitrogen oxides NOx Motor vehicle and furnace exhaust radiation from passing out into space,

thus causing the global temperature to Visual Inf Ozone O Motor vehicle exhaust 3 rise.

Sulphur dioxide SO2 Coal-fired power stations © Diagram © Diagram Visual Information Ltd. ● ● of nitrogen 3 ● ● nitrogen 2 ● ● molecule 1 triple bond solubility nitrogen group 5 Key words (945.4 kJmol the unreactivenatureofnitrogen. at 100°C. NH nitrite: ammonium chlorideandsodium best madewhenitisneededbymixing because itdecomposesovertime.Itis Ammonium nitriteisdifficulttostore NH decomposition ofammoniumnitrite: bythether Nitrogen isformed of nitrogenfallsfrom2.3cm increasing temperature.Thesolubility The nitrogen areweak. forcesin that theintermolecular range oftemperature.Thisindicates nitrogen isonlyaliquidoversmall low,nitrogen arebothvery and The meltingpointandboilingof N Nitrogen existsasnitrogenmolecules, Nitrogen needed tobreakthe A bond. atoms areheldtogetherbyatriple provides threeelectrons.Thenitrogen water at0°Cto1.0cm nordertofilltheshell. in require anadditionalthreeelectrons electrons intheouterorbitaland table. Nitrogenatomshavefive Nitrogen atomand Laboratory preparation Physical propertiesof 2 NH PATTERNS—NON-METALS , 4 4 in whicheachnitrogenatom Cl(s) +NaNO NO solubility 4 NO 2 (s) large amountofenergyis 2 is (s) +NaCl(s) ➞ in -1 2H group 5 of gasesdecreaseswith ), whichaccountsfor 70 2 2 O(g) +N (s) N ➞ 3 ϵ of per 100gwater N the periodic 2 triple bond (g) 3 per 100g mal 2 Nitrogen Nitrogen properties Physical chloride andsodium nitrate 3 1 Physical properties ofnitrogen c a Nitrogen atom andmolecule Laboratory preparation of nitrogen from ammonium Nitrogen atom, m.p./°C 10–9 .7nn none none 0.97 –196 –120 NNN b 14 7 Nitrogen molecule, N N b.p./°C (relative density to air) oo smell color e d c b a water nitrogen sand tray heat nitrate insolution ammonium chlorideandsodium e 2 solubility 1.52 cm of water in 100g at STP d 3 71

Other methods of PATTERNS—NON-METALS preparing nitrogen Key words ammonia group 8 1 Extraction of nitrogen from the atmosphere inert nitrogen c f soluble a Other methods ● In addition to preparing nitrogen from ammonium chloride and sodium nitrate, it can be extracted from the air d d or from the reduction of copper(II) oxide by ammonia. h 1 Extraction of nitrogen from the atmosphere ● Air is approximately 80 percent nitrogen and 20 percent oxygen. b g Impure nitrogen can be obtained by removing carbon dioxide and oxygen e from air. ● Potassium hydroxide solution reacts with carbon dioxide:

KOH(aq) + CO2(g) ➞ KHCO3(aq) ● A hot copper pile reacts with oxygen:

2Cu(s) + O2(g) ➞ 2CuO(s) ● Nitrogen prepared in this way contains 2 Preparation of nitrogen from ammonia argon and other group 8 gases. However, because these are chemically j f i inert, they would not interfere with any subsequent reactions. 2 Preparation of nitrogen from ammonia ● Ammonia can be used to reduce d d copper(II) oxide to copper. Nitrogen is one of the other products of this reaction:

h 3CuO(s) + 2NH3(g) ➞ 3Cu(s) + 3H2O(g) + N2(g) ● Nitrogen is not very soluble and is readily collected over water. g ● Water vapor condenses in the water trough. Ammonia is very soluble, and unreacted ammonia dissolves in the e water. mation Ltd. or a air intake g water b potassium hydroxide solution to absorb carbon h nitrogen collected over water c hot copper coil to remove oxygen i dry ammonia gas Visual Inf d heat j dry copper(II) oxide e safety trap f delivery tube © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● ● ● ● Nitrogen cycle nitrogen cycle nitrogen nitrite nitrate ammonia Key words Ammonia bacteria: the plants. chemicals. Animalssubsequentlyeat N denitrifying bacteria. denitrifying conver Nitrogen compoundsinthesoilare mak the soilbyplants,whichusethemto Nitrogen compoundsaretaken outof growing plantswithessentialnitrogen. far Ammonium nitrateiswidelyusedby fer added tosoilasartificial Nitrogen compoundsmayalsobe nitrates into decay processesisconverted the soil,ammonia decay ofdeadplantsandanimals.In animal wasteproductsandbythe the soilasaresultofdecay Nitrogen compoundsarereleasedinto root nodulesofsomeplants. by nitrogen-fixingbacteriafoundinthe conver Atmospheric nitrogenisalso to thegroundasrain. in theatmosphereandeventuallyfall These oxidesdissolveinwatervapor N example: nitrogenoxides.Forreact, forming atmospheric nitrogenandoxygento Lightning providestheenergyfor processes. between thesoilandairbynatural Nitrogen 2 2 ➞ PATTERNS—NON-METALS (g) +2O (g) +O mers andgardenerstoprovide e Nitrites proteins andotheressential ted tonitrogengasby ted intonitrogencompounds by theactionofnitrif is continuallybeingrecycled 2 ➞ (g) 2 (g) ➞ Ammonium compounds ➞ Nitrates ➞ 72 2NO(g) 2NO 2 formed during formed (g) tilizers. ying The nitrogencycle 5 4 3 2 1 however, cannot use nitrogen directly from theatmosphere. All plants andanimalsneednitrogen, present inproteins andnucleicacids. Most livingthings, Nitrogen cycle schematic Nitrogen cycle bacteria andfungi. wastes are converted to ammoniaby The proteins indead organisms andinbody Animals eat plant proteins. Plants use nitrogen for makingproteins. some plant roots. Nitrogen intheatmosphere istrapped by Nitrogen intheair. 2 1 7 8 3 7 3 4 2 1 8 8 7 6 Plants absorb thenitrates. fertilizer. nitratesArtificial areaddedto thesoil as nitrates. Other bacteria convert theammonia to 6 6 4 5 5 73

Preparation and PATTERNS—NON-METALS properties of ammonia Key words alkali lone pair ammonia shell 1 Laboratory preparation of ammonia ammonium hydroxide d bond angle a 1 Laboratory preparation of ammonia ● Ammonia is formed by the reaction of an ammonium compound, such as ammonium chloride, with an alkali, such as sodium hydroxide:

NH4Cl(s) + NaOH(aq) ➞ NH3(g) + NaCl(aq) + H2O(l) ● Ammonia gas is dried by passing it through a column of calcium oxide. b 2 Bonding angle ● The five electrons in the outer electron shell of nitrogen plus three e shared electrons from the hydrogen atoms form three pairs of bonding a sodium hydroxide c electrons and one pair of non-bonding b ammonium chloride electrons (lone pair). c heat d calcium oxide for drying ● The four pairs of electrons are e downward displacement of air directed toward the corners of a tetrahedron. However, repulsion between the non-bonding pair of 2 Bonding angle electrons and the bonding pairs of electrons forces the nitrogen–hydrogen bonds slightly closer to each other, resulting in a bond angle of 107°. By comparison, N N the bond angle in methane is 109.5°. H H H H 3 Physical properties of 107° ammonia ● Ammonia is less dense than air and is H H collected by upward delivery (downward displacement of air). ● Ammonia is exceptionally soluble and 3 Physical properties of ammonia cannot be collected over water. 680 cm3 of ammonia will dissolve in Physical property Ammonia 1 g of water at 20°C. ● Ammonia dissolves in water to form a Ammonia –77.7 solution that is a weak alkali:

NH3(g) + H2O(l) Carbon monoxide –33.5 + - NH4 (aq ) + OH (aq) Methane 0.59 ● Ammonia solution is sometimes mation Ltd.

referred to as ammonium hydroxide. or Nitrogen oxides colorless

Ozone characteristic unpleasant odour Visual Inf

Sulphur dioxide 68 000 cm3 in 100 g of water © Diagram © Diagram Visual Information Ltd. ● ● ammonia withtemperature 3 ● ● ammonia withpressure 2 ● ● ● ● 1 Le Chatelier’s equilibrium ammonia Key words reaction ofnitrogenandhydrogen. change. position willaltersoastoopposethe system at concentration andpressure)ofa conditions (suchastemperature, mixture willcontainmoreammonia. temperature, sotheequilibrium to opposethedecreasein position willmovetotherightinorder for decrease intemperaturewillfavorthe principle,a According toLeChatelier’s given out. heatis The reactionisexothermic; more ammonia. the equilibriummixturewillcontain to opposetheincreaseinpressure,so position willmovetotherightinorder reaction.Theequilibrium forward an increaseinpressurewillfavorthe principle, According toLeChatelier’s pressure. moles ofproduct reactants reaction,fourmolesof In theforward if According to out. reaction iscarried pressure andtemperatureatwhichthe equilibrium mixturedependsonthe The concentrationofammoniainthe N Backward reaction: N Forward reaction: The reactionisreversible. Ammonia Reversible reaction Variation ofpercent Variation ofpercent principle 2 2 any changeismadetotheexter PATTERNS—NON-METALS (g) +3H (g) +3H ward reaction.Theequilibrium equilibrium are converted intotwo are converted is 2 2 (g) 2NH (g) made industriallybythe Le Chatelier’s principle Chatelier’s Le ➞ 74 so 2NH reactant product there isadropin , 3 3 (g) the equilibrium (g) nal , 1 process): theory ammonia (theHaber Industrial preparationof 3 2 N Equilibrium % of ammonia Equilibrium % of ammonia Reversible reaction 2 Variation ofpercentammoniawithtemperature Variation ofpercentammoniawithpressure 100 100 80 80 40 40 60 90 60 90 20 20 50 50 30 30 (g) +3H 70 70 10 10 0 0 2 0 0 400 200 5 4 oe 2moles moles 0 300 100 0 300 100 2 (g) 2NH 0 400 200 Temperature (°C) Pressure (atm) 3 g (g) ∆ of catalyst Working range H = with temperature Variation of %ammonia –92 kJmol 200°C 100°C 25 atm 50 atm 100 atm 200 atm 400 atm 400°C 500°C 300°C –1 75

Industrial preparation of PATTERNS—NON-METALS ammonia (the Haber Key words ammonia hydrocarbon catalyst hydrogen process): schematic equilibrium nitrogen fractional distillation

The process ● The raw materials for the Haber Hydrocarbons Liquid air process are hydrogen and nitrogen. ● Hydrogen is obtained by the steam reforming of hydrocarbons, such as methane, or the reaction of steam with coke.

CH4(g) + H2O(g) CO(g) + 3H2(g) C(s) + H2O(g) CO(g) + H2(g) ● Nitrogen is obtained from the fractional distillation of liquid air. Hydrogen Nitrogen ● The formation of ammonia is favored Steam Fractional by high pressure, and the reaction is normally carried out at 80–110 atm. It reforming distillation is also favored by low temperature, but this also lowers the rate of reaction, so a catalyst is used. The reaction is normally carried out at 370–450°C in the presence of a finely divided iron catalyst. ● In reality, the reaction is not allowed to Reactor reach equilibrium.A single pass through the reactor results in about 15 Temperature: percent conversion to ammonia. 370–450°C ● The reaction mixture is cooled to Pressure: below the boiling point of ammonia, at 80–110 atm which point liquid ammonia condenses out and is removed. The Catalyst: mixture of unreacted hydrogen and iron nitrogen is recycled back into the reactor. ● Around 80 percent of the ammonia produced each year is used to make fertilizers, including ammonia solution, ammonium nitrate, ammonium sulfate, and urea.

Liquid Cooling Unreacted ammonia below –33.5°C hydrogen and nitrogen mation Ltd. or Visual Inf © Diagram © Diagram Visual Information Ltd. ● 2 ● ● ● ● ● ● ● ● 1 nitric acid exothermic azeotropic ammonia Key words oxides. absorption oftheresultingnitrogen fer ammonium nitrate, whichisusedasa production isdirectedtomaking Over twothirdsofnitricacid and giveconcentratednitricacid. is usedtoreducethewatercontent distillation. Concentratedsulfuricacid nitric cannotbeobtainedby nitric acidbymass.Thus,concentrated composition) containing68.5percent boils withoutachangein azeotropic mixture Nitric acidandwaterform concentration. demand isforacidofthis acid bymass.Mostofthemodern typically contains55–60percentnitric The acidfromtheabsorptiontowers to producenitricacid. Dinitrogen tetroxidereactswithwater subsequently, dinitrogentetroxide. order tomak Air isaddedtothenitrogenoxidesin nitrogen: which ammoniaisoxidizedto minimize acompetingreactionin Conditions arecarefullycontrolledto quantity ofheatisproduced. , The reactionisexothermic ammonia isoxidized: platinum–rhodium gauzeandthe ammonia andairispassedthrougha In oxidation acid The industrialproductionof 4NH 3N 2NO(g) +O 4NH 2NO Preparation Uses ofnitricacid mixture ⌬ 4HNO PATTERNS—NON-METALS the converter, amixtureof tilizer andinexplosives. 2 = H O 3 2 3 involves twostages:the (g) +5O 4 (g) N (g) +3O (g) +2H -909 kjmol 3 (aq) +2NO(g) of 2 (g) 2NO 2 e ammonia O 2 2 (g) 4NO(g)+6H 2 (g) 2N nitrogen dioxideand, 4 O(l) (g) 76 -1 oxidation (a mixturethat 2 2 (g) and the (g) +6H an and alarge nitric 2 2 O(g) O(g) of nitricacid Industrial preparation 2 1 d a b Industrial manufacture of nitricacid Summary of uses c Ammonium nitrate 79% f e aromatics Nitro 12% f e d c b a k j i h g NO, NO oxidation reaction platinum rhodiumcatalyst power ammonia air unreacted gas nitric acid pump reaction withwater water g Adipic 2 acid , 9% h O 2 j k i 77

Nitrogen: reactions in PATTERNS—NON-METALS ammonia and nitric acid Key words ammonia nitric acid 1 Redox chemistry (ammonia) oxide oxidizing agent reducing agent 2NH3 + 3Cl2 N2 + 6HCl Ammonia reduces chlorine to hydrogen chloride and nitrogen 1 Redox chemistry (ammonia) 2NH3 + 3CuO 3Cu + 3H2O + N2 ● Ammonia is a reducing agent and will Ammonia reduces copper oxide to copper, water, and nitrogen reduce chlorine and heated metal oxides such as copper oxide. During the reactions, the ammonia is oxidized 2 Redox chemistry (nitric acid) to nitrogen.

C + 4HNO3 CO2 + 4NO2 + 2H2O 2 Redox chemistry (nitric acid) Concentrated nitric acid oxidizes carbon to carbon dioxide ● In addition to its properties as an acid, nitric acid is also a powerful oxidizing

3Cu + 8HNO (dilute) 3Cu(NO ) + 4H O + 2NO → 3 3 2 2 agent. It is able to oxidize both non- Dilute nitric acid oxidizes copper to produce copper nitrate, water, and nitrogen oxide metals and metals. 3 Complex ammonia salts Cu + 4HNO3(conc) Cu(NO3)2 + 2H2O + 2NO2 → ● When ammonia solution is added drop Concentrayed nitric acid oxidizes copper to produce copper nitrate, water, and nitrogen dioxide by drop to copper(II) sulfate solution, a pale blue precipitate of copper(II) hydroxide is formed: 2+ - 3 Complex ammonia salts Cu (aq) + 2OH (aq) ➞ Cu(OH)2(s) ● When an excess of ammonia solution ammonia is added, the pale blue precipitate solution redissolves, forming a deep blue solution:

Cu(OH)2(s) + 4NH3(aq) ➞ 2+ [Cu(NH3)4] ● The deep blue solution contains the complex ion tetraamminecopper(II), 2+ pale blue [Cu(NH3)4] . precipitate ● Ammonia also forms complex ions with other metals, such as + Ammonia solutionis added More ammonia solution The precipitate diasppears, diamminesilver(I), [Ag(NH3)2] and to CuSo4 solution is added leaving a deep royal blue [Ni(NH ) ]2+ solution (a complex salt) hexaamminenickel(II), 3 6 . 4 Tetraamminecopper(II) 4 Tetraamminecopper(II) ion ● In the tetraamminecopper(II) ion, a copper ion is surrounded by four ammonia molecules in a square planar X arrangement. The non-bonding pair of electrons on each nitrogen atom is X attracted to the central positively A charged copper ion. mation Ltd.

X or

X Visual Inf Square planar © Diagram © Diagram Visual Information Ltd. ● ● ● ● 4 ● ● ● 3 ● ● ● ● ammonia 2 ● metals 1 nitrite nitric acid nitrate ammonia acid Key words oxide. wateranddinitrogen heating, forming Ammonium nitratedecomposeson dioxide, andoxygen. metaloxides,nitrogen heating toform Other metalnitratesdecomposeon to for lithium nitrate)decomposeonheating Group 1metalnitrates(apar All metal (3D). nitrogen dioxidewhenreactingwitha Hot, concentratednitricacidproduces metal (3C). nitrogen oxidewhenreactingwitha Cold, dilutenitricacidproduces and apower Nitric acidisbothastrong(3A) produce Ammonia reactswithoxygento produce ametalandnitrogen(2C). Ammonia reactswithan produce a Ammonia reactswithan produce asolublealkalinegas(2A). Ammonia metals, suchassodiumandhydrogen. metals, suchasmagnesium,andnon- Nitrogen With metalsandnon- Nitric acid Basic reactionsof Nitrates PATTERNS—NON-METALS nitrates m metal nitric acid combines directlywithboth salt reacts withwaterto r eysolubleinwater. are very ful nitrites (2B). oxidizing agent(3B). 78 salt oxidizing agent oxide nitrogen (2D). and oxygen. oxide acid t to form to 3B 3A 2D complexingagent 2C ammoniawithoxygen tomakenitricacid 2B reducingagent 2A solublealkalinegas nitrogen Basic reactionsof C B A 4 B A 3 D and then C B A 2 1 oxidizing agent strong acid With metalsandnon-metals Nitric acid Basic reactionsofammonia Nitrates NH NH N 4NO Cu +4HNO NH 2Pb(NO 2NaNO C HNO Cu(OH) 2NO +O 4NH 2NH 6Na +N 3Mg +N 2 + 3 3 4 + NO 2HNO 3 3 2 + + 3 3H + + + + C NH HCl H 3 3 2 O 3 CO3Cu +3H 3CuO 2 5O 2 2 H 2 2 ) + ONH 2 2 2 3 + OH 2 4NH 3 2H 2 3 F 4HNO O e catalyst CO Cu(NH 2NO 4NO +6H 2NH 2Na Mg 2H 2PbO 2NaNO Cu(NO 4A 4C 4B 3 O group 1(excluding LiNO ammonium nitrate others 2 2 3 4 4 O N 3 Cl + + 3 2 + N

2 + + + 3 + 2NO 3 3 2 ) ) OH NO N 4NO 4 2 2+ + 2 2 2 + O O +2OH O 2 3 2 O - – 2H 2 2 + + + H N 2 O O 3 2 2 ) O 2 - + 2NO 2 79

Nitrate fertilizers PATTERNS—NON-METALS

Key words 1 Atmospheric nitrogen alkali nitric acid Nitrogen → Ammonia → Nitric acid amino acid protein ammonia chlorophyll neutralization Ammonium nitrate

NH3(aq) + HNO3(aq) → NH4NO3(aq) 1 Atmospheric nitrogen ● Atmospheric nitrogen is an important raw material in the manufacture of 2 Ammonia nitrate ammonia and nitric acid. ● Ammonia solution is alkali, while Formula mass of ammonium nitrate = 14 + 4 + 14 + 3 × 16 = 80 nitric acid is acidic. 2 × 14 × 100 ● The two solutions undergo a Percentage of nitrogen in ammonium nitrate = = 35% 80 neutralization reaction to form the salt ammonium nitrate. 2 Ammonia nitrate 3 Nitrogen in plants ● The percentage of nitrogen in a nitrogenous fertilizer is an important R CH3 CH CH3 factor in determining how much CC fertilizer should be used on an area of H2NCH COOH crops. animo acids HC CC CH ● Ammonium nitrate is very soluble in water. Any excess that is applied to soil H C 3 N is readily washed out into streams and C C C CH *CH proteins 3 rivers, where it causes environmental H N Mg N problems.

H C C C C CH2CH3 3 Nitrogen in plants N ● Plants use nitrogen to make amino acids and, from these, to make CH2 CC C CH proteins. ● CH HC CC Plants also use nitrogen to make other 2 important chemicals, such as C chlorophyll. O CH O C CH3 O 4 Nitrogen fertilizers CH CH ● Ammonium sulfate is formed by the neutralization reaction between C20H39 CH3 ammonia solution and sulfuric acid: 2NH3(aq) + H2SO4(aq) ➞ Chlorophyll a (NH ) SO (aq) (In chlorophyll b, the methyl group 4 2 4 marked by an asterisk is replaced ● Urea is a waste product of animal by a —CHO group) metabolism and is excreted from the body in sweat and urine. It is made industrially by the reaction of 4 Table of nitrogen fertilizers ammonia with carbon dioxide. This reaction is carried out at 200 °C and Compound Formula Percentage of nitrogen 200 atmospheres: CO (g) + 2NH (g) ➞ mation Ltd. 2 3 or Ammonium nitrate NH NO 35.00 4 3 H2NCONH2(l) + H2O(g) Visual Inf Ammonium sulphate (NH4)2SO4 21.21

Urea H2NCONH2 46.67 © Diagram © Diagram Visual Information Ltd. ● oxygen andsulfur 3 ● ● ● ● of oxygen 2 ● ● ● 1 oxygen group 6 enzyme double bond catalyst Key words atoms, molecule composedofeightsulfur crown. bond, atoms areheldtogetherbyadouble provides twoelectrons.Theoxygen yellow solid. colorless, odorlessgas,whilesulfurisa At roomtemperature,oxygen isa of hydrogen peroxideyields20volumes strength. For example,20-volume in solutionsdesignatedbyvolume Hydrogen peroxideisusuallysupplied be collectedoverwater. Oxygen isonlyslightlysolubleandcan hydrogen peroxide. decompose upto50,000moleculesof second, onemoleculeofcatalasecan including the decomposed byavarietyofcatalysts, Hydrogen peroxideisrapidly 2H such asmanganesedioxide: peroxide usingasuitable by thedecompositionofhydrogen Oxygen ispreparedinthelaboratory A O Oxygen existsasoxygenmolecules, Oxygen electrons tofilltheshell. electron shellandrequiretwo element havesixelectronsintheouter of theperiodictable.Atoms ofeach Atoms andmolecules Physical propertiesof Laboratory preparation t 2 PATTERNS—NON-METALS , oxygen gaspervolumeofsolution. room temperature,sulfurexistsasa 2 O in whicheachoxygenatom 2 (l) O=O S and 8 ➞ , arranged intheshapeofa arranged . O sulfur 2 enzyme (g) +2H 80 are bothingroup6 sulfur catalase. Inone 2 O(l) catalyst, 3 Oxygen andsulfur 2 1 Solubility Smell Density g/dm Color b.p./°C m.p./°C Physical properties ofoxygenandsulfur Atoms andmolecules a b Laboratory preparation of oxygen Physical properties Sulfur atom Oxygen atom 3 S O 32 16 16 S 8 d c b a O oxygen water solid catalyst –manganese oxide liquid reactant –hydrogen 0.007g per100g/H none none 1.31 –183 –218 Oxygen Oxygen molecule O SS 2 Sulfur molecule S O O SS SS (crown-shaped) S S almost insoluble slight yellow 2070 444 119 O 2 8 d Sulfur c 81

Extraction of sulfur— PATTERNS—NON-METALS the Frasch process Key words ore sulfide The Frasch process sulfur sulfur dioxide

Processing and uses a ● Hot compressed air and superheated steam are piped underground. This forces water and molten sulfur to the c surface. ● The sulfur obtained is about 99.5 percent pure, and may be stored b and transported molten or allowed to cool and solidify. ● A significant proportion of the elemental sulfur used in industry is obtained as a by-product of other industrial processes such as the refining of metal sulfide ores and d petroleum refining. ● In petroleum refining, sulfur compounds like thiols (R-SH) and disulphides (R-S-S-R) are removed e from some of the petroleum fractions because they would damage the catalysts used in refining processes 150m and also because of their potential to cause environmental problems. For f example, if they were not removed from fuels like gasoline, they would g burn to form sulfur dioxide. This gas dissolves in water in the atmosphere, forming an acid, and would significantly increase the acidity of rain water. ● Sulfur compounds are converted to hydrogen sulfide by catalytic hydrogenation:

R-SH(g) + H2(g) ➞ h R-H(g) + H2S(g) R-S-S-R(g) + 3H2(g) ➞ 2R-H(g) + 2H2S(g) ● Hydrogen sulfide can be converted to sulfur using the Claus process:

6H2S(g) + 5O2(g) ➞ 2SO2(g) + 2S2(g) + 6H2O(g) 4H2S(g) + 2SO2(g) ➞ 3S2(g) + 4H2O(g) mation Ltd. or a hot compressed air e quicksand b superheated water (at 170°C) f sand Visual Inf c molten sulfur and water g limestone d clay h sulfur © Diagram © Diagram Visual Information Ltd. ● ● ● 3 ● ● ● ● 2 ● ● ● 1 ● Allotropes oxygen diatomic bond allotrope Key words which iscalled exists asatriatomicmolecule, moving, andtheviscosityfalls. sulfur molecules,whicharefree- linked breaks,yielding small structure On causing asharpincreaseinviscosity. These moleculesjoinbycross-linking, break open,yieldingsulfurmolecules. On alow- around, forming the sulfurmoleculesareabletomove Sulfur meltswhengentlyheated,and indifferentways. arranged puckered molecularrings,but Each allotropeiscomposedofS8 like andhaveadeeperyellow color. areneedle- Monocline sulfurcrystals yellow appearance. havealemon- Rhombic sulfurcrystals and monoclinesulfur. includingrhombicsulfur solid form, Sulfur hasseveralallotropesinthe of electrons,whiletheotherdoesnot. of theotheratomsalsodonatesapair bond withtheothertwoatoms.One a donates apairofelectronstoform In ozone,thecentraloxygenatom electron toeachbond. atoms. Eachatomdonatesone Oxygen hastwo diatomic molecule ofoxygenisa The mostcommonform oxygen state. Manyelements,including same elementinthephysical Allotropes one allotrope. Oxygen Heating sulfur Sulfur molecule PATTERNS—NON-METALS even strongerheating,thecross- stronger heating,thesulfurrings and are different forms ofthe are differentforms sulfur ozone 82 bonds , , exist asmorethan viscosity sulfur ozone O . 2 . viscosity between the The gasalso O liquid. 3 , 3 allotropes Oxygen andsulfur: Viscosity State of matter Color Structure 2 1 Allotrope ofoxygen Allotropes ofsulfur Rhombic sulfur O OO yellow Oxygen solid – O yellow liquid low O O ++ O O liquid – Monoclinic high red Ozone sulfur O O – O O O liquid black low 83

Oxygen and sulfur: PATTERNS—NON-METALS compound formation Key words hydrogen oxide hydrogen oxygen 1 Oxygen and magnesium 2 Reaction of sulfur and iron peroxide peroxide hydrogen sulfide sulfide magnesium sulfur

Mg2+ Fe2+ 1 Oxygen and magnesium a ● Oxygen reacts with most metals to form metal oxides. Magnesium burns in air with a bright flame, producing a white smoke of magnesium oxide. The reaction is even more vigorous in pure 2– 2– b O S oxygen:

2Mg(s) + O2(g) ➞ 2MgO ● Soluble metal oxides dissolve in water to form alkaline solutions: Oxygen reacts with Magnesium oxide Sulfur and iron Iron sulfide is MgO(s) + H2O(l) ➞ Mg(OH)2(aq) magnesiun is ionic glow also ionic 2 Sulfur and iron 3 Phosphorous reacts with atmospheric oxygen ● Sulfur forms sulfides with many metals. When iron and sulfur are heated together, iron sulfide is formed: d h 8Fe + S8 = 8FeS g 3 Oxygen and phosphorous c f ● Oxygen also reacts with non-metals to form oxides. Phosphorus burns in air to form phosphorus(V) oxide. Approximately 20 percent of the air is used: e P4(s) + 5O2(g) ➞ P4O10(s) ● Non-metal oxides dissolve in water to A tube full of air Phosphorus is added Unreacted phosphorus form acids: is left behind P4O10(s) + H2O(l) ➞ 4H3PO4(aq) a oxgen d 100 cm3 of air g phosphorus reacting b magnesium burning e water h 79 cm3 of air is left behind 4 Other common reactions c volume scale f stiff wire ● Hydrogen burns in oxygen to form water:

4 Water, hydrogen peroxide, and hydrogen sulfide 2H2(g) + O2(g) ➞ 2H2O(l) ● Hydrogen peroxide is formed by the H H H H H reaction of metal peroxides, such as barium peroxide, with dilute acids: ➞ O O O S BaO2(s) + H2SO4(aq) H2O2(aq) + BaSO4(s) H ● Hydrogen sulfide is formed by the HH H H H reaction of a metal sulfide with a dilute acid: FeS(s) + 2HCl(aq) ➞

O OO S FeCl (aq) + H S(g) mation Ltd. 2 2 or H Water is formed when Hydrogen peroxide is made Hydrogen sulfide is made Visual Inf oxygen and hydrogen by reacting a metal by the reaction of a metal are exploded together peroxide with acid sulfide with dilute acid © Diagram © Diagram Visual Information Ltd. ● ● SO 3 ● ● ● of sulfurtrioxide 2 ● ● ● sulfur dioxide 1 ● Sulfur oxides sulfur sulfite oxide lone pair catalyst Key words bonds for In sulfurtrioxide,thethreedouble are atanangleof120°. between thesulfurandoxygen atoms shape inwhichthedoublebonds other aspossiblebyadoptingabent electrons arekept asfarfrom each around thesulfuratom.Thepairsof bonding or of bondingelectronsandanon- In sulfurdioxide,therearefourpairs H sulfuricacid: form Sulfur trioxidedissolvesinwaterto whencooled. crystals needle-likeSulfur trioxideforms 2SO asbestos in thepresenceofaplatinized sulfur dioxideandoxygenareheated whendry Sulfur trioxideisformed H for Sulfur dioxidedissolvesinwaterto and collectedbydownwarddelivery. through anhydrouscalciumchloride Sulfur dioxideisdriedbypassingit Na dioxide: react withdiluteacidstofromsulfur Metal oxide. oxide) and two Sulfur bond angleisalso 120°. around thesulfuratominwhich the Laboratory preparationof Laboratory preparation 2 2 2NaCl(aq) +H PATTERNS—NON-METALS O(l) +SO O(l) +SO 2 m SO 2 oxides: (g) +O sulfurous acid 2 sulfites 3 combines withoxygentofor (s) +2HCl(aq)➞ and SO catalyst: a m sulfur trioxide lone pair 3 2 sulfur dioxide 2 (g) (g) , (g) 2SO trigonal planarstr such assodiumsulfite, 84 2 ➞ ➞ O(l) +SO 3 H H : sulfur trioxide sulfurous acid sulfur dioxide 2 2 molecules SO SO of electrons 3 (g) 4 3 (aq) (aq) (sulfur(VI) 2 (sulfur(IV) (g) ucture m e d c b a The oxidesofsulfur oxygen upward displacement anhydrous CaCl sodium sulfite dilute 2 1 3 e f g a b Laboratory preparation of sulfurdioxide SO Laboratory preparation of sulfurtrioxide oeueo ufrdoieMolecule of sulfurtrioxide Molecule of sulfurdioxide 2 O and SO 2 S 3 l molecules O OOO h g f 120° plantinized asbestos for drying concentrated sulfuricacid sulfur dioxide S c O h i j l k j i 3-way tap to thefumecupboard needles of sulfuroxide salt freezing mixture of ice and S O d O 120° O S k O 85

Industrial preparation of PATTERNS—NON-METALS sulfuric acid (the contact Key words catalyst sulfuric acid exothermic sulfur trioxide process): theory equilibrium sulfur sulfur dioxide 1 Sulfur burning –1 Preparation of sulfuric acid S(1) + O2(g) → SO2(g) ∆H = –297 kJ mol ● The industrial preparation of sulfuric acid is a three stage process: 1. Sulfur burning 2 Conversion 2. Conversion of sulfur dioxide to sulfur trioxide –1 3. Absorption of sulfur trioxide to form 2SO2(g) + O2(g) 2SO3(g) ∆H = –192 kJ mol sulfuric acid. 4 moles 2 moles 1 Sulfur burning SO O 2 2 ● Molten sulfur is sprayed into a furnace 420°C and burned in a blast of dry air. The reaction is very exothermic, and the Reaction bed 1 reaction temperature rises to over 1,000°C. The mixture of gases, 600°C 63% conversion containing sulfur dioxide and oxygen, is cooled before conversion. 450°C 2 Conversion Reaction bed 2 Heat ● The conversion of sulfur dioxide into exchangers sulfur trioxide is an exothermic 510°C 84% conversion reaction. The forward reaction is favored by a low temperature. 450°C However, this would also reduce the 98% H SO 2 4 rate of reaction, so it would take Reaction bed 3 longer for the reaction mixture to reach equilibrium. SO3 ● 475°C 93% conversion The reaction is carried out at Intermediate temperatures between 420–620°C in absorber 420°C the presence of a vanadium(V) oxide remaining catalyst. SO Reaction bed 4 3 ● Modern converters consist of four reaction beds. The reaction mixture is 99.5% H SO 435°C 99.5% conversion 2 4 cooled after passing through each of the first two beds in order to maximize conversion in subsequent beds. 3 Absorption ● SO3(g) Sulfur trioxide is removed and to final absorber absorbed after the reaction mixture has passed through both the third and fourth beds. 3 Absorption ● Sulfur trioxide is absorbed into mation Ltd.

98 percent sulfuric acid to form or 99.5 percent sulfuric acid, which is H2SO4(1) + SO3(g) H2S2O7(1)

sometimes referred to as oleum and Visual Inf H S O (1) + H O(1) → 2H SO (1) given the chemical formula H2S2O7. 2 2 7 2 2 4 ● Oleum is then diluted to give 98

percent sulfuric acid. © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● ● ● Preparing sulfuricacid sulfur dioxide sulfur sulfide ore catalyst Key words trioxide. conversion of the reactionmixturefor there issufficientoxygenremainingin ground orasaby obtained eitherdirectlyfromthe refining ofcr refining ofmetal industrial processes,suchasthe soaps, andphosphatic fertilizers. paints andpigments, detergentsand the manufacture ofgeneralchemicals, usesinclude of industries.Important Sulfuric acidisusedinawidevariety stack. the atmosphereathighlevelvia a sulfuric acidbeforebeingreleased into The gasesarefilteredtoremoveany oxygen andtracesofsulfurdioxide. of together withasmallproportion absorption consistsmostlyofnitrogen, The mixtureofgasesthatremainaf beds. fourth produced betweenthethirdand and byremovingthesulfurtrioxide removing heatbetweenreactionbeds reasons. Thiscanonlybeattainedby for botheconomicandenvironmental dioxide tosulfurtrioxideisessential A about 0.6mdeep. consisting ofalayercatalystpellets there fourreactionbeds,each converter,reaction beds.Inamodern per The catalystpelletsarepacked onto is generallyinthefor It potassium sulfateonasilicasupport. pentoxide) The vanadium(V)oxide(vanadium An excessofdr manufacture of The between 420–620 an optimumworkingtemperature is inactivebelowabout380°Candhas sur cylindrical pelletsthatensurealarge conversion of99.5percentsulfur PATTERNS—NON-METALS face areaforreaction.Thecatalyst forated plate supports toform forated platesupports sulfur needed forthe catalyst ude oil. sulfur dioxide y sulfuric acid 86 air isusedtoensure ufd ores sulfide -product ofother °C. is activatedby sulfur trioxide sulfuric acid m ofsmall to and the is sulfur ter process): schematic sulfuric acid(thecontact Industrial preparationof Sulfur Water Industrial preparation of sulfuricacid Catalyst: Pressure: Temperature: Reactor Absorbtion into 98% sulfuric 99.5% sulfuric (V) oxide vanadium atmosphere more than a 420–620°C little acid acid Dilution burning Sulfur SO SO sulfuric acid 3 2 Product , + 98% S0 0 2 2 + depleted air sulfur dioxide 95% nitrogen Waste gases 5% oxygen exchangers Excess dry air Heat 87

Affinity of concentrated PATTERNS—NON-METALS sulfuric acid for water Key words alcohol sulfuric acid alkene 1 Sulfuric acid and atmospheric water carboxylic acid catalyst ester H2O H2O atmospheric water H2O 1 Sulfuric acid and H O atmospheric water 2 several days ● Concentrated sulfuric acid will absorb H O H2O concentrated 2 H2O later water from the air. sulfuric acid ● The level of liquid in a beaker H2SO4 H2SO4 containing concentrated sulfuric acid rises as water is absorbed and the acid becomes more dilute. 2 Illustrating sulfuric acid’s affinity for water steam 2 Sulfuric acid’s affinity sulfuric acid for water added ● Concentrated sulfuric acid will remove the elements of water from organic

chemicals such as sucrose (C12H22O11). mass of ● When concentrated sulfuric acid is carbon poured onto sucrose, the crystalline white sucrose turns into a black amorphous mass of carbon. sucrose 3 Drying gases Reaction with Reaction with atmospheric water sugar solution ● Concentrated sulfuric acid can be used to dry gases, such as hydrogen. The gas is bubbled through the acid in a 3 Drying gases suitable container. ● Some gases, such as ammonia, react wet dry with concentrated sulfuric acid and gas gas cannot be dried in this way. 4 Forming esters and alkenes ● Concentrated sulfuric acid is used as a catalyst in the formation of esters from carboxylic acids and alcohols. concentrated Concentrated sulfuric acid removes sulfiric acid the elements of water from alcohols to form alkenes:

-H2O R-CH2-CH2OH ➞ R-CH=CH2

4 Forming esters and alkenes O O –H O

2 mation Ltd.

RC RC or OH H OR1 OR1 Visual Inf

Carboxylic acid Alcohol Ester © Diagram © Diagram Visual Information Ltd. ● ● ● ● reactions 2 ● ● ● ● ● ● 1 oxidizing agent hydrogen hydrogen Key words to asulfate: to aqueous solution.Itreducesiron(III) as itisinthesulfate. hydroxide, andcarbonateisthe same on themetalioninoxide, or reductiontak In allofthesereactions,nooxidation dioxide, andwater salts,carbon carbonates toform Sulfuric acidreactswithmetal sulfatesandwater hydroxides toform Sulfuric acidreactswithmetal to for Sulfuric acidreactswithmetaloxides Cu is metal tocopper(II).Thesulfuricacid oxidizing agent,copper concentrated sulfuricacidactsasan sulfuric acid.Inthisreaction,the Copper reactswithconcentrated sulfur trioxidebyreactionwith Sulfur dioxidecanbeoxidizedto Fe both inthegaseousfor Sulfur dioxide power agent butisitselfoxidizedbyamore Hydrogen peroxide S Cl oxidized toelemental to chlorideions.Thesulfideis Hydrogen sulfide Oxidation potassium manganate(VII). oxidized atthesametime. substance isreducedandanother they cannotoccurinisolation.One described as reactions aremoreaccurately Common redoxreactions Sulfuric acidandsulfate sulfide peroxide 2- 2 itself reducedtosulfurdioxide: PATTERNS—NON-METALS 3+ iron(II) whilebeingitselfoxidized ➞ ➞ + e + m 2e Cu + S ful oxidizingagentsuchas - sulfates andwater. - 2+ ➞ ➞ 2e reactions and + 2Cl Fe - redox reactions 2e 2+ sa is - - 88 es oxidation reduction oxidation reduction reduces chlorinegas place. Thecharge reducing agent is anoxidizing sulfur dioxide sulfur reduction redox reaction oxygen sulfur m andin reduction : because oxygen . oxidation andreduction Oxygen andsulfur: cd+mtlcroae=Salt + carbon dioxide +water = H Acid +metal carbonate Salt +water = H Salt +water Acid +metal hydroxide = H Acid +metal oxide Concentrated sulfuricacidoxidizes copper Cu + 2H Oxygen oxidizes sulfurdioxide O Sulfur oxide reduces iron chloridesolution SO Hydrogen peroxide reduces potassium manganate(VII) solution H Hydrogen sulfide reduces chlorinegas 8H 1 2 Common redoxreactions 2 2 2 2 2 Sulfuric acidandsulfate reactions SO O SO SO 2 2 + S 2 + 2SO 4 4 4 + + 2FeCl + + + 3KMnO 8Cl 2 ZnCO Cu(OH) MgSO MgO SO 2 2 4 3 + 3 4 2H 2 2 2FeCl O CUSO 2SO 2KOH +2MnO S ZnSO CuSO 8 + 3 16HCl 4 2 4 4 4 + + + + + 2HCl +H CO 2H H H 2 2 O 2 O 2 O + + 2 H + SO 2 2O O 2 SO 2

→ 2 4 89

Basic reactions of PATTERNS—NON-METALS oxygen Key words alkali oxygen amphoteric transition metals 1 Reactions cation valency hydroxide Oxidizes other elements oxide 2H2 + O2 2H2O 4Na + O2 2Na2O 1 Reactions 2Na + O Na O ● Oxygen reacts with both metals and 2 2 2 non-metals to form oxides. S8 + 8O2 8SO2 ● Group 1 and group 2 metals often P + 5O P O form more than one oxide: 4 2 4 10 Na2O sodium monoxide Na2O2 sodium peroxide 2Cu + O2 2CuO NaO2 sodium dioxide Oxidizes other elements ● Transition metals form oxides in 2CO + O2 2CO2 which the metal exhibits different valency states: 2SO2 + O2 2SO3 Cu2O copper(I) oxide 4NH + 5O 4NO + 6H O CuO copper(II) oxide 3 2 2 ● Non-metallic elements also form more than one oxide: 2 The hydrides P4O6 phosphorus(III) oxide Water P4O10 phosphorus(V) oxide a 2Na + 2H O 2NaOH + H 2 2 → 2 The hydrides + – b H2O + HCl H3O + Cl ● Water reacts with group 1 and group 2 metals to give the metal hydroxide c + – H2O + NH3 NH4 + OH and hydrogen. In these reactions, the metal is oxidized to a metal cation and d H2O + CO2 H2CO3 the water is reduced: H2O + SO2 H2SO3 M ➞ M+ and M ➞ M2+ ● In the Brønsted-Lowry theory of acids Oxidizes other elements

→ and bases, an acid is defined as a e BaO2 + H2SO4 H2O2 + BaO4 substance that donates protons and a base as a substance that accepts f H O + 2FeCl + 2HCl 2FeCl + 2H O 2 4 2 3 2 protons. Water acts as both an acid g H2O2 + 2KMnO4 2KOH + 2MnO2 + 2O2 and a base. ● Non-metallic oxides dissolve in water to form acids: + - 3 The oxides H2CO3 H + HCO3 carbonic acid + Oxidizes other elements H2SO3 H + HSO3 sulfurous acid h CuO + H2SO4 CuSO4 + H2O 3 The oxides i ZnO + H2SO4 ZnSO4 + H2O ● Metal oxides are basic and react with acids to form salts and water. ZnO + 2NaOH Na2Zn(CH)4 + H2O ● Non-metallic oxides are acidic or Oxidizes other elements neutral. ● j SO , CO Some metal oxides are amphoteric: 2 2 they react with both acids and alkalis. mation Ltd.

k H2O, CO or a oxidizes reactive metals e preparation i amphoteric Visual Inf b accepts protons from acids f an oxiding agent j acidic c gives protons to bases g a reducing agent k neutral d reacts with non-metal oxides h basic © Diagram © Diagram Visual Information Ltd. ● ● 4 ● ● ● 3 ● ● ● 2 ● ● ● 1 redox reaction oxidizing agent hydrogen sulfide dehydrating Key words hydrogen sulfide: sulfides reactwithacidstogive water ortheelementsof dehyrating agent Concentrated sulfuricacidisa strong metals andnon-metals. oxidizing agent Concentrated sulfuricacidisastrong for Sulfur trioxidedissolvesinwaterto trioxide. Sulfur dioxideisoxidizedtosulfur sulfurousacid,aweakacid. form Sulfur dioxidedissolvesinwaterto elemental sulfur undergo a Hydrogen sulfideandsulfurdioxide Pb sulfide: oflead sulfide duetotheformation black inthepresenceofhydrogen Moist lead(II)ethanoatepaperturns characteristically coloredprecipitates. are onlysparinglysolubleandform water, however, othermetalsulfides Group 1metalsulfidesaresolublein for Hydrogen sulfidedissolvesinwaterto sulfuric acid reaction betweenconcentrated Sulfur dioxide as oxygenandchlorine. Sulfur combineswithnon-metalssuch FeS(s) +2HCl(aq)➞ hydrogen tofor Sulfur Reactions ofsulfur The oxidesSO The hydrides agent The hydroxycompound FeCl PATTERNS—NON-METALS 2+ m a m S + sulfuric acid,astrongacid. 2 reacts withmostmetalsand (aq) +H weak acid. 2- redox reaction ➞ PbS and sulfur. is formed bythe is formed 2 m . 90 S(g) and willoxidizeboth and willremove sulfides sulfuric acid sulfur dioxide sulfur sulfide 2 and SO . to form Metal . 3 Basic reactionsofsulfur As adehydrating agent As anoxidizing agent As astrong acid 4 SO Is reducing agent Is asparingly soluble acidicgas 3 Causes precipitation of insoluble metel sulfides Is areducing agent Reduces some compounds Is asparingly soluble acidicgas 2 Reduces other elements elements Oxidizes some elements 1 Reactions of sulfur The oxides SO The hydrides 3 The hydroxy compound CuSO C CH Cu +2H 2H H SO SO 2SO SO CuSO 2H H 3S +2H 2S +Cl Cu S FeS H 2Cu +S Fe +S is very acidic 12 2 2 2 + SO S 2 2 3 2 2 3 H + SO S CH O 2 + + + + 22 S 4 4 4 2 + + O H H H .5H 2H 4 2 + + 2 SO O H CH OH 11 2 2 2 2 2 + O O O H SO SO H

2 2 2 S C 2 2 2 O O 2 S 4 4 and SO –11H H H –5H H 170°C 2 2 2 SO SO SO 3 2 2 O O 4 4 4 H CuS +H 12C CO 3S +2H H H 2SO 2H 3SO S SO CuSO H CuSO H

2 2 2 3 2 3

O O SO SO S → 2 2 2

2 2 S O → + + 2 3 2 + = 4 3 4 4 + + + → 2SO CH + + HS HSO 3S 2H SO

2 2 2

O SO – 2 → 2 4 2 –

→ O 4 → + + 2H 2H 2 O 2 O 91

The halogens: group 7 PATTERNS—NON-METALS

Key words 1 Electron structure astatine fluorine bromine halogens F 2 7 chlorine iodine covalent bond ionic compound covalent Cl 8 7 compound

Br 2 18 7 Halogens ● The elements of group 7 are sometimes referred to as the halogens. I 2 8 18 7 They are flourine, chlorine, bromine, iodine, and astatine. The symbol ‘X’ is inner electrons outer shell often used to denote a halogen atom and ‘X-’ a halogen ion. 1 Electron structure ● All halogen atoms have seven 2 Halogen atom and molecule electrons in their outer shell. A halogen atom needs one more electron to fill the outer shell, and it can obtain this either by forming a single covalent bond or by forming an X ion, X-. Halogens form both covalent compounds and ionic compounds. 2 Halogen atom and Halogen atom molecule ● Halogens exist as diatomic molecules. Each atom in the molecule provides a single electron to form a covalent bond. The result is that each atom has X X control over eight electrons. 3 Physical properties ● There is a gradation of physical properties going down group 7. Halogen molecule 1. State changes from solid to liquid to gas. Bromine is one of only two elements that exist as liquids at room 3 Physical properties temperature. 2. The color darkens from pale yellow Element FluorineChlorine Bromine Iodine to black. 3. Melting point and boiling point Atomic number 9 17 35 53 increase. Relative atomic mass 19.0 35.5 79.9 126.9 ● There is a gradual decrease in chemical reactivity going down State at 20°C gas gas liquid solid group 7. ● Fluorine oxidizes water to give oxygen: Color pale yellow pale green red-brown black 2F2 + 2H2O ➞ 4HF + O2 ● Chlorine reacts less vigorously with mation Ltd. m.p./°C –220 –101 –7 113 or water, forming an acidic solution:

b.p./°C –188 –35 59 183 C2 + H2O HCl + HOCl Visual Inf ● Bromine and iodine form solutions in Solubility/g per 100g reacts readily 0.59 (reacts 3.6 0.018 of water at 20°C with water slightly water, although the latter is not very

soluble. © Diagram © Diagram Visual Information Ltd. ● ● of 3 ● ● of bromine 2 ● ● ● of chlorine 1 oxidation iodine distillation chlorine bromine Key words dioxide (manganese(IV)oxide): oxidizing agent hydrochloric acidusingasuitable the and thenbacktosolidoncooling. changes directlyfromsolidto vapor mixture bysublimation.Onheating, it Iodine isremovedfromthereaction MnO concentrated sulfuricacid: situ bromine. Hydrogeniodideismade Iodine distillation removed fromthereactionmixtureby bromineis Because itboilsat59°C, MnO chlorine: Bromine Ca(OCl) powder, usingdilutehydrochloricacid: frombleaching made inthelaboratory Chlorine canalsobeconveniently by downwarddeliver more densethanairandiscollected thegas.Chlorineis sulfuric acidtodry and thenthroughconcentrated to removeanyhydrogenchloridegas, The gasisfirstpassedthroughwater MnO Chlorine Laboratory preparation Laboratory preparation Laboratory preparation CaCl MnCl MnSO MnSO iodine PATTERNS—NON-METALS oxidation by reactingsodiumiodidewith 2 2 2 (s) +2KI(aq)2H (s) +2NaBr(aq)2H (s) +4HCl(aq)➞ + 2H 2 2 is madeinasimilarwayto (aq) +2H 2H 4 4 2 (aq) +2H 2 (aq) +K (aq) +Na (s) +4HCl(aq)➞ O(l) +I is is madeinasimilarwayto 2 . O(l) +Br made inthelaborator of concentrated 92 2 such asmanganese 2 2 (g) 2 O(l) +2Cl SO 2 O(l) +Cl SO oxidizing agent 2 4 y. (g) (aq) + 4 (aq) 2 SO 2 2 4 SO 2 (g) (aq) (g) 4 (aq) y by ➞ in ➞ of thehalogens Laboratory preparation 3 2 1 q a b r Laboratory preparation of chlorine Laboratory preparation of iodine Laboratory preparation of bromine k l c m s t d n t s q p o p m l k j i h g f e d c b a cold water warm gently + manganese oxide +potassium iodine bromine fumes of HBr cold water warm gently manganese oxide +sodium bromide concentrated sulfuricacid water hydrogen gas chlorine gas concentrated brine chlorine gas concentrated H water to remove HClfumes warm gently manganese dioxide concentrated hydrochloric acid concentrated H e o 2 SO 2 SO 4 to dryCl 4 p 2 f 93

Compounds of chlorine PATTERNS—NON-METALS

Key words 1 Chlorine and metals chloride hydrogen Calcium burns Aluminum reacts when chlorine chloride in chlorine warmed in a stream of covalent sodium chloride chloride aluminum compound sulfuric acid halide chlorine white smoke

chlorine 1 Chlorine and metals ● Metals, such as calcium, burn in calcium chlorine to produce the to fume corresponding metal chloride: cupboard Ca(s) + Cl2(g) ➞ CaCl2(s) heat ● Aluminum reacts with chlorine to form aluminum chloride:

2Al(s) + 3Cl2(g) ➞ 2AlCl3(s) ● Unlike many metal chlorides, 2 Laboratory preparation of hydrogen chloride aluminum chloride is hydrolyzed by concentrated sulfuric acid water, giving off hydrogen chloride gas:

AlCl3(s) + 3H2O(l) ➞ Al(OH)3(s) + 3HCl(g) It is for this reason that aluminum halides fume when they come into contact with moist air. hydrogen chloride 2 Laboratory preparation sodium chloride of hydrogen chloride ● Hydrogen chloride is made by the reaction of sodium chloride with concentrated sulfuric acid: 3 Compounds with non-metals NaCl(s) + H2SO4(aq) ➞ NaHSO4(s) + HCl(g) Cl Cl Cl Cl P 3 Compounds with Cl S C S non-metals Cl Cl ● Cl Cl Chlorine forms covalent compounds with non-metals such as carbon,

Carbon tetrachloride (CCl4) Phosphorus trichloride (PCl3) Sulfur monochloride (S2Cl2) phosphorus, and sulfur. 4 Pesticides H H 4 The structure of some C C ● chlorinated pesticides Chlorinated compounds provide a ClC C range of pesticides. C C Cl ● DDT, BHC, Aldrin, and Dieldrin have Dichlorophenyl- H H trichloroethane H CC Cl been the source of environmental (DDT) H H concern, and their use is now C C Cl prohibited or severely restricted. ClC C H Cl C C HH H H C Cl H Cl H Cl C C Cl Cl C H C H Cl C H C H

C C C C C C mation Ltd. H CCH CCl2 CH2 CCl2 CH2 O or C C C C C C C

Cl Cl Cl C H C H Cl C H C H Visual Inf H Cl Cl H Cl H Benzene hexachloride (BHC) Aldrin Dieldrin © Diagram © Diagram Visual Information Ltd. ● ● ● In 2 ● ● ● In 1 ● Hydrogen chloride hydrogen covalent covalent bond carbonate Key words become achlorideion, the chlorineatomgainsanelectronto showing thatitisanacid: red andreactswithcarbonates, bluelitmuspaper The solutionturns achargethroughthesolution. to carry conducts electricity. Theionsareable The solutioncontainsionsand becomeahydrogenion, to The hydrogenatomlosesanelectron chloride becomesanioniccompound. In showing thatitisnotanacid. litmus paperoron The solutionhasnoeffectonblue does notconductelectricity. The solutioncontainsnoionsand covalent bond. the each donateoneelectrontoform hydrogen atomandthechlorine remains acovalentcompound.The methylbenzene, hydrogenchloride In solutioninorganicsolventssuchas compound compound. Itbecomesan solvents, itremainsacovalent compound Hydrogen chloride Na chloride compound 2NaCl(aq) +CO PATTERNS—NON-METALS aqueous solution,hydrogen 2 CO organic solvents aqueous solution 3 (aq) +2HCl(aq)➞ . in aqueoussolutions. In solutionsinorganic 94 2 (g) +H carbonates gas isa ionic compound ion Cl - 2 . O(l) ionic covalent H + , , and thus in solution Hydrogen chloride 2 1 In organicsolvents In aqueoussolution H–Cl H–Cl H–Cl H H + Cl + – Cl Cl – – H–Cl H–Cl Cl H H – + + H H Cl Cl 95

Acid/base chemistry PATTERNS—NON-METALS of the halogens Key words halide oxidizing agent hydrochloric acid reducing agent 1 Laboratory preparation of hydrochloric acid hydrogen silver nitrate chloride nitric acid

1 Laboratory preparation of a a a hydrochloric acid ● Hydrochloric acid is made in the b laboratory by dissolving hydrogen chloride gas in water. ● Hydrogen chloride is very soluble in water. It is dissolved by passing through an inverted filter funnel, the rim of which sits just below the water level. When water is sucked into the funnel, the water level drops, and the funnel rim is no longer submerged. This prevents water being sucked back into the apparatus. Hydrogen chloride enters The level in the The cycle water via a filter funnel beaker drops starts again 2 Solubility of the halogens ● All halogens are oxidizing agents. a hydrochloric acid (HCl) b plug of liquid in funnel However, oxidizing power decreases down the group: fluorine > chlorine > bromine > iodine 2 Solubility of the halogens ● Halide ions are reducing agents. The reducing power increases down the 2F2 + 2H2O 4HF + O2 group: Flouorine is so reactive it decomposes water producing hydrofluoric acid and oxygen fluorine < chlorine < bromine < iodine Cl + H O HCl + HOCl 2 2 3 Chloride test Chlorine is the next most reactive halogen after fluorine ● The presence of halide ions in solution can be detected by adding a few drops of dilute nitric acid followed by 3 Chloride test several drops of silver nitrate solution. 1. Chloride ions form a white precipitate of insoluble silver chloride: Ag+(aq) + Cl-(aq) ➞ AgCl(s) solution 2. Bromide ions form a cream precipitate of insoluble silver bromide: Ag+(aq) + Br-(aq) ➞ AgBr(s) 3. Iodide ions form a yellow precipitate of insoluble silver iodide: Ag+(aq) + I-(aq) ➞ AgI(s)

silver nitrate Dissolve unknown substance, Colored precipitation

solution adding dilute nitric acid to proves presence of mation Ltd. the solution. Add a few drops chloride, bromide, or of silver nitrate solution or iodine Visual Inf © Diagram © Diagram Visual Information Ltd. ● ● ● 4 ● ● ● 3 ● chloride 2 ● 1 reactivity series oxidizing agent noble gases chlorine chloride Key words with hydrogen. illustrated atright bytheirreaction in The relativereactivitiesofthehalogens iodine. directly withchlorine,bromine, or nitrogen, andoxygendonotreact andsulfur,phosphorus butcarbon, Chlorine reactsdirectlywith gases. except nitrogenandmostofthe Fluorine oxidizesmostnon-metals low inthereactivityseries even iodinewillslowlyoxidizemetals metals decreasesdownthegroup,but The easewithwhichhalogensoxidize 2Fe(s) +3Cl chloride isproduced: a reactive metals.Whenironisheatedin Chlorine oxidizesallbuttheleast gold andsilver, easily. Fluorine oxidizesallmetals,including Halogens readilyoxidizemetals. 2FeCl reduced to of iron(III).Thechlorineatomsare yellow-brown, showingtheformation the colorchangesfromgreento bubbled intoiron(II)chloridesolution, iron(II) toiron(III).Whenchlorineis Chlorine canalsobeusedtooxidize 8H reduced tohydrogenchloride: chlorine gainshydrogenandis removing hydrogen.Intur and oxidizesthehydrogensulfideby Chlorine are mixed,elementalsulfur When hydrogensulfideandchlorine Calcium andchlorine Halogens andmetals Chlorine andferrous Halogens andnon-metals stream of dry chlorine,iron(III) stream ofdry PATTERNS—NON-METALS redox reactions 2 S(g) +8Cl 2 (aq) +Cl acts asanoxidizingagent chloride 2 (g) 2 (g) 2 96 (g) ➞ ➞ with non-metalsis 2FeCl ➞ sulfur redox reaction ions: S 2FeCl 8 (s) +16HCl(g) 3 (s) . n, the 3 is formed. (aq) noble 4 halogens Redox reactionsofthe 2 1 3 gas hydrogen sulfide plate chlorine gas H H H H Halogens andnon-metals 2 2 2 2 dry chlorine Calcium burnsinchlorine (g) +Cl (g) +F (g) +I (g) +Br Halogens andmetals Reaction of chlorinewithferrous chloride chlorine gas solution green iron chloride 2 2 (g) Chlorine gas andhydrogen 2 (g) 2 sulfide gas are separated (g) (g) Reaction → → → → 2Hl(g) 2HF(g) 2HCl(g) 2HBr(g) by plate Chlorine gas ispassed into ferrous chloridesolution slow even when heated needs heat andacatalyst explosive insunlight butslow inthe dark explosive heat Plate isremoved iron(III) chloride Observations Yellow-brown iron chloride solution inside gasjars sulfur coating plate 97

Reactivity of the halogens PATTERNS—NON-METALS

1 Chemical reactivity of halogens with each other Key words displacement Chlorine Bromine Iodine reaction halide halogens Chloride immiscible

1 Reactivity of halogens Bromide ● The chemical reactivity of the halogens decreases down group 7: fluorine > chlorine > bromine > Iodide iodine ● A more reactive halogen will displace the ions of a less reactive halogen from a metal halide solution. This is called a displacement reaction. ● Chlorine will displace bromide ions 2 Reaction of chlorine and bromine and iodide ions from solution. ● Bromine will displace iodide ions from solution. ● In a displacement reaction, the halogen acts as an oxidizing agent and is reduced while the halide ion is oxidized. colorless solution of orange solution of chlorine in hexane bromine in hexane 2 Chlorine and bromine ● Chlorine dissolves in the organic solvent hexane to give a colorless or colorless aqueous colorless aqueous slightly green solution, depending on solution containing solution containing K+ and Br– ions K+ and Cl– ions concentration. ● Hexane is immiscible with water. When the two liquids are mixed, hexane forms a layer above water. shaking ● When solutions of chlorine in hexane and potassium bromide in water are shaken together, chlorine displaces bromide ions from the aqueous 3 Reaction of chlorine and iodine solution. Bromine is more soluble in hexane than in water, and an orange layer of bromine in hexane forms:

2KBr + Cl2 ➞ 2KCl + Br2 - - 2Br + Cl2 ➞ 2Cl + Br2 3 Chlorine and iodine ● When solutions of chlorine in hexane colorless solution of pink/purple solution and potassium iodide in water are chlorine in hexane of iodine in hexane shaken together, chlorine displaces iodide ions from the aqueous solution. Iodine is more soluble in hexane than colorless aqueous colorless aqueous solution containing solution containing in water, and a pink-purple layer of + – + – mation Ltd.

K and I ions K and Cl ions iodine in hexane forms: or 2KI + Cl2 ➞ 2KCl + I2 2I- + Cl ➞ 2Cl- + I

2 2 Visual Inf shaking © Diagram © Diagram Visual Information Ltd. ● ● 3 ● ● 2 ● ● ● ● and uranium 1 lead iron gold copper aluminum Key words Russia Russia, Europe,Angola,Australia South Africa, Europe,Russia Russia America Zinc Iron Copper W Aluminum Uranium Platinum Silver: Gold Central andSouthAfrica, Australia Gold, sliver,platinum, Iron, zinc,andlead Aluminum andcopper est Africa, Russia,India,Australia th andSouthAmerica, : frica, USA,Canada, : and PATTERNS—METALS Nor South A USA, SouthAmerica th America,Centraland : Nor : th America,Europe, lead frica, USA,South : Nor South A : South America,Jamaica, : USA, Europe,A 98 zinc uranium silver platinum ustralia, of metals World distribution 3 2 1 Gold, sliver,platinum,anduranium zinc and lead iron uranium platinum silver gold copper aluminum Iron, zinc,andlead Aluminum andcopper 99

Main ores of metals PATTERNS—METALS

Metal Chemical name Formula of ore(s) Key words Common name for ore(s) grade for ore(s) mineral ore aluminum oxide bauxite aluminum oxide Al2O3.2H2O sulfide

chromium Ores chromite iron chromium oxide FeCr O 2 4 ● An ore is a mineral from which a metal (or non-metal) can be extracted. copper ● Metal ores are often metal oxides or chalcopyrite copper iron sulfide CuFeS2 metal sulfides. bornite copper iron sulfide Cu5FeS4 ● A metal may be present in a range of chalcocite copper(I) sulfide Cu2S different minerals, but not all minerals will be suitable sources of that metal. Recovering ores iron ● To be appropriate for mining, an ore haematite iron(III) oxide Fe O 2 3 must contain minerals that are magnetite iron(II)iron(III) oxide Fe3O4 valuable and that are concentrated enough to be mined profitably. It must lead also be economically viable to extract galena lead(II) sulfide PbS the ore from waste rock. ● Mineral deposits that are economically cerussite lead(II) carbonate PbCO3 recoverable are called ore deposits. anglesite lead(II) sulfate PbSO4 Not all mineral deposits are suitable for recovery. Some may be too low in magnesium grade (the concentration of the ore in magnesite magnesium carbonate MgCO3 the rock) or technically impossible to extract. mercury cinnabar mercury sulfide HgS Formation ● The process of ore formation is called silver ore genesis. ● argentite silver sulfide Ag S Ore genesis involves a variety of 2 geological, internal, hydrothermal, metamorphic, and surficial processes. sodium salt sodium chloride NaCl

tin

cassiterite tin oxide SnO2

titanium

rutile titanium oxide TiO2 ilmenite iron titanium oxide FeTiO3

uranium

uraninite uranium oxide UO2 mation Ltd. or zinc

zinc blende zinc sulfide ZnS Visual Inf

calamine zinc carbonate ZnCO3 © Diagram © Diagram Visual Information Ltd. ● 3 ● 2 ● ● 1 orbital melting point group 1 boiling point alkali metals Key words in apar spherically symmetric;porbitalspoint different shapes:sorbitalsare nucleus. Differentorbitalshave gradually increasingdistancefromthe series of electron. Orbitalsaregroupedina there isahighprobabilityoffindingan third shell. second shell,and1sorbitalinthe first shell,2sand6porbitalsinthe indicates, sodiumhas2sorbitalsinthe Thus,asthetable orbital structure. describe anatombydescribingthe have complicatedshapes.Scientists known ofitschemistr the hardnessdecreases. increases, thedensityand point Reading downthegroup, orbitals inaseriesof of anatomarearranged thenucleus The electronssurrounding because itis considered whendiscussingthegroup periodic table.However, itisnot Francium liesbelowcesiuminthe andcesium. potassium, rubidium, The elementsincludelithium,sodium, with watertogivealkalinesolutions. alkali metals Historically column oftheperiodictable. The Position inperiodictable Physical properties Electron-shell structure group 1 PATTERNS—METALS decreases, theboilingpoint ticular direction;anddorbitals , shells areas aroundtheatomwhere , theywereknownasthe radioactive metals occupythefirst because theyallreact 100 (energy levels)ata shell radioactive y. , and littleis melting compared withatypical metal 3 2 1 The group1metals Na Rb Cs rnF 5030 804511300 4–5 7860 3000 1530 Fe Iron Typical metal Cesium Rubidium Potassium Sodium Lithium element Group 1 Li K Position intheperiodictable Cs Rb K Na Li Physical properties of group Ielements Electron-shell structure down thegroup metal reactivity increases energy level 1s 1s 1s 1s 1s 2 2 2 2 2 across aperiod metal reactivity decreases Cs Rb K Na Li 2s 2s 2s 2s 2s 1 m.p./°C 2 2 2 2 2p 2p 2p 2p 180 98 64 29 39 6 6 6 6 3s 3s 3s 3s 1s 2 2 2 1 b.p./°C 3p 3p 3p 1336 700 669 883 759 6 6 6 4s 4s 4s 2 1 2 /g cm 3d 3d Density 0.86 0.97 0.53 1.88 1.53 2 10 10 4p 4p –3 6 6 5s 5s Hardness number ofelectrons /Moh 1 2 0.2 0.3 0.5 0.4 0.6 4d type oforbital 10 in orbital 5p Conductivity 6 Ω 6s 23800 –1 16400 11700 2000 9100 cm 1 –1 101

The group 1 metals: PATTERNS—METALS sodium Key words acid cathode acid-base electrolysis 1 Reaction of sodium hydroxide (NaOH) 2 Sodium burns indicator salt with hydrochloric acid (HCl) readily in chlorine alkali titration anode or oxygen

pipette 1 Reaction of NaOH with HCl burette ● Group 1 hydroxides are alkalis. They can be used to form salts by blue Hydrochloric neutralizing them with acids in a indicator acid process call titration. Sodium chloride is made by neutralizing sodium hydroxide with hydrochloric acid.

NaOH + HCl ➞ NaCl + H2O ● sodium chloride A given volume of sodium hydroxide indicator turns solution is put into a conical flask. green ● sodium A few drops of an acid–base indicator hydroxide are added to the sodium hydroxide solution solution. The indicator is a different Sodium hydroxide color in acids and alkalis. solution is placed Hydrochloric acid ● Hydrochloric acid is run into the in the beaker is introduced into sodium hydroxide solution burette the sodium hydroxide solution until the indicator just changes color. Results of the 2 Burning sodium reaction ● Sodium burns vigorously in chlorine to form sodium chloride:

3 Sodium reacts with nitrogen gas 2Na + Cl2 ➞ 2NaCl sodium ● Sodium also burns vigorously in oxygen to form sodium oxide: nitrogen 4Na + O2 ➞ 2Na2O 3 Sodium and nitrogen ● When heated in a stream of nitrogen, heat sodium reacts to form sodium nitride:

6Na + N2 ➞ 2Na3N 4 Commercial preparation of sodium 4 Preparation of sodium ● chlorine gas Sodium is obtained by the electrolysis of molten sodium chloride in a Downs cell. Sodium is discharged at the negative electrode (cathode): Na+ + e- ➞ Na liquid sodium The product at the positive electrode molten sodium (anode) is chlorine gas: chloride - - 2Cl ➞ Cl2 + 2e circular cathode mation Ltd. or

anode Visual Inf © Diagram © Diagram Visual Information Ltd. ● ● 3 ● ● ● 2 ● ● 1 ion group 2 alkaline earth Key words ber metals alkaline earth group 2metalswereknownasthe Consequently outer electronsfromthenucleus. become progressivelymorereactive. outer twoelectrons,andthemetals less energyisneededtoremovethe because itisradioactive considered whendiscussingthegroup lies belowbarium,isnotusually which strontium, andbarium.Radium, include ber column oftheperiodictable.They metals inthesame periodisless. however, thereactivityofgroup2 asgroup1metals; chemical properties The group2metalshavesimilar increases goingdownthegroup. reactivity As withthegroup1metals, electrons, whichpar between thenucleusandouter there aremorelayersofelectrons the positivelychargednucleus,and2) from two outerelectronsarefurther ionization energyintwoways:1)the electrons. Thisaffectsthevalueof increase inthenumberof Going downthegroup,thereisan first electronandthesecondelectron. i.e., theenergyneededtoremove first andsecond needed todothisisthesumof losing twoouterelectrons.Theenergy All group2elementsfor (see page150). describing itselectron-shellstr Scientists candescribeanatomby down thegroup. size oftheatomsincreasesgoing The atomicradiusand,therefore,the The alkaline solutions. Position inperiodictable Reactivity Electron-shell structure metals yllium reactwithwatertogive group 2 PATTERNS—METALS of thegroup2metals yllium, magnesium,calcium, metals occupythesecond , going downthegroup, 102 ionization ener reactivity radioactive orbital ionization energy tially shieldsthe because allbut . m Historically orbitals ions ucture by gies, of , The group2metals 2 1 3 Ba Sr Ca Mg Be Position intheperiodictable Electron-shell structure Reactivity comparison withgroup I Mg Ba Be C Sr a energy level 1s 1s 1s 1s 1s 2 2 2 2 2 2s 2s 2s 2s 2s 2 4 2 3 2 2 2 2 2p 2p 2p 2p across aperiod reactivity decreases going 6 6 6 6 aMg Na iBe Li 3s 3s 3s 3s KCa I 1s 2 2 2 2 3p 3p 3p 6 6 6 4s 4s 4s 2 2 2 II 3d 3d 2 10 10 4p 4p going down agroup reactivity increases 6 6 5s 5s number ofelectrons 2 2 4d type oforbital 10 in orbital 5p 6 6s 2 103

The group 2 metals: PATTERNS—METALS general reactions Key words alkali limewater carbonic acid soluble group 2 1 Sodium and water 2 Calcium and water hydrochloric acid insoluble

1 Sodium and water ● Sodium reacts vigorously with water to form sodium hydroxide solution (a strong alkali) and hydrogen gas. 2 Calcium and water pH = 7 pH = 12 pH = 7 pH = 10 bubbles bubbles ● Calcium reacts less vigorously with water than sodium to form calcium 2Na + 2H2O = Solution Ca + 2H2O = Suspension 2Na(OH) + H2 Ca(OH)2 + H2 hydroxide solution and hydrogen gas. → → ● Calcium hydroxide is less soluble than sodium hydroxide and forms a weak 3 Production of “rainwater” 4 Effect of rainfall on alkali solution containing suspended fresh water particles of undissolved solid. rain 3 Rainwater ● CO2 gas CO2 + H2O = H2CO3 Naturally occurring rainwater is always weakly acidic because carbon dioxide from the air dissolves in it, forming

weak carbonic acid, H2CO3. 4 Effect of rainfall ● What rain flows over rocks, group 2 metal compounds dissolve in it, resulting in water that contains dissolved solids. limestone ● Magnesium and calcium carbonates rocks are effectively insoluble in water, but stream of water containing they react with rainwater, because it is Bubble unknown Result if the dissolved solids acidic, to form soluble gas into limewater gas is CO2 rocks with soluble group 2 compounds Ca(OH ) hydrogencarbonates. 2 (e.g., CaCl2, CaSO)

5 Ca(OH)2 test ● 5 Calcium hydroxide 6 Barium chloride (BaCl2) Limewater, an aqueous solution of [Ca(OH)2] test for carbon test for metal sulfates calcium hydroxide, is used to test for dioxide gas carbon dioxide. ● When carbon dioxide is bubbled into limewater, it turns milky due to the Gas milky formation of insoluble calcium suspension carbonate, CaCo3. CaCO3 6 BaCl2 test ● The test solution is first acidified with dilute hydrochloric acid, and a few mation Ltd.

drops of barium chloride solution are or Add barium chloride A white suspension then added. If the solution contains dissolved in is produced if the sulfate ions, a white precipitate of Visual Inf Result if the Bubble unknown hydrochloric acid solution contains barium sulfate is formed. gas into limewater gas is CO2 to the known a sulfate Ca(OH2) solution © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● ● transition metals Characteristics of shell oxidation state orbital catalyst actinides Key words The fillingisnotalwaysregular. which fillupgoingacrossaperiod. of shells haveincompletelyfilled breaking), density material canwithstandwithout tensile strength Transition metals tendtohavehigh out light. move betweenenergylevels,giving electrons inthe3dorbitalsthatcan compounds becausetheirionscontain T and 4sorbitals(seetable). with additionalelectronsfillingthe3d that oftheelementargontogether elements inperiod4canbewrittenas ofallthe The electronicstructure transition metals. orbitals arecloseinthefirstseriesof energy levelsofthethirdandfourth progressively closerinenergy successive electronshellsbecome Moving awayfromthenucleus, transactinides. (ununbium), isthe series, from103(lawrencium)to112 (mercur elements 71(lanthanum)to80 (cadmium), isinperiod5.Thethird, series, elements39(yttrium)to48 (zinc) andisinperiod4.Thesecond element 21(scandium)to30 from series, showninthetable,runs organized intofourseries:Thefirst The 40transitionalmetalsare inner electronicstr metallic elementswithanincomplete The different boiling points.Theyhaveavariety of electrons, theirnext-to-outer outermost ransition metals often havecolored ransition metalsoften ten good transition metals PATTERNS—METALS y), isinperiod6.Thefour oxidation states shell catalysts. 104 (the maximumstressa contains atmosttwo , andmelting ucture. Whilethe actinides transition metals tensile strength are anyofthe and are most . and The orbitals th , become closer inenergy Note: Astheshellsof electrons get from andfurther further thenucleussuccessive shells (Ar) =electron structure of argon elements from scandiumto zinc Table to show theelectron structures of atoms andionsof electron structure The transitionmetals: agns n(Ar)3d Mn Manganese (Ar)3d Cr Chromium (Ar)3d Sc Scandium Electronic Common Electronic Symbol Element icZ (Ar)3d Zn Zinc (Ar)3d Cu (Ar)3d Copper Ni (Ar)3d Nickel Co Cobalt (Ar)3d Fe Iron iaimT (Ar)3d Ti Titanium aaimV(Ar)3d V Vanadium fao of ion structure ion of atom structure 6 5 5 3 2 1 10 10 8 7 4s 4s 4s 4s 4s 4s 4s 4s 4s 4s 2 2 2 2 1 2 2 2 2 1 Fe Fe Mn Cr V Ti Sc Zn Cu Cu Ni Co 3+ 4+ 2+ 3+ 2+ 3+ 3+ 2+ 2+ + 2+ 2+ (Ar) (Ar)3d (Ar)3d (Ar)3d (Ar)3d (Ar)3d (Ar)3d (Ar)3d (Ar)3d (Ar)3d (Ar)3d (Ar) 10 9 10 8 7 5 6 5 3 2 105

The transition metals: PATTERNS—METALS ionization energies and Key words boiling point conductor physical properties ionization energy melting point transition metals 1 Graphs showing the second and third ionization energies of the elements from scandium to zinc 1 Ionization energies ● Ionization energy is the energy 4000 Zn needed to remove an electron from a third ionization energy neutral gaseous atom or ion against Cu the attraction of the nucleus. 3500 Ni ● The second ionization energy is the Mn Co energy needed to go from M+ to M2+, Cr (where M = metal), and the third 3000 V ionization energy is the energy needed 1

– 2+ 3+ l Fe to go from M to M .

o Tc

m ● The second ionization energy J K 2500 increases across period 4 because there is an increasing positive charge Sc on the nucleus of the ion, making it Cu increasingly more difficult to remove 2000 Ni the second electron. Co ● The third ionization energy for all Cr Fe Mn Zn elements is significantly higher than 1500 V Ti second ionization energy the second. Removal of the second Sc electron results in a greater net difference between the positive charge 1000 on the nucleus of the ion and the negative charge surrounding it, so it requires more energy to remove a 500 third electron. 2024283222 26 30 Atomic number 2 Physical properties ● Like other metals, transition metals are good conductors of both heat and 2 Physical properties of the elements from scandium to zinc electricity. ● The transition metals in general have Element Atomic m.p./°C b.p./°C Density/ Ionic radius/nm higher melting points and boiling radius/nm gcm–3 M2+ M3+ points than groups 1 and 2 metals. ● The atomic radii and ionic radii for the Scandium Sc 0.16 1540 2730 3.0 0.081 M2+ ion decrease across period 4 Titanium Ti 0.15 1680 3260 4.5 0.090 0.076 because the increasing positive charge on the nucleus of the atom and of the Vanadium V 0.14 1900 3400 6.1 0.088 0.074 ion provides a greater attraction for Chromium Cr 0.13 1890 2480 7.2 0.084 0.069 the surrounding electrons. Manganese Mn 0.14 1240 2100 7.4 0.080 0.066 Iron Fe 0.13 1540 3000 7.9 0.076 0.064

Cobalt Co 0.13 1500 2900 8.9 0.074 0.063 mation Ltd. or Nickel Ni 0.13 1450 2730 8.9 0.072 0.062 Visual Inf Copper Cu 0.13 1080 2600 8.9 0.070 Zinc Zn 0.13 420 910 7.1 0.074 © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● 2 ● ● ● ● 1 cryolite amphoteric aluminum alkali acid Key words transfer tetrahydroxoaluminate(III), is aluminum. the orecanbeprocessedtoobtain replaced atregular intervals. gradually eatenawayandmust be dioxide. Thegraphiteanodeis the oxygenproducedtogivecarbon The graphiteanodereadilyreacts with Oxide ionsareoxidizedtooxygen. molten fromthebottomofcell. aluminum metal,whichistappedoff Aluminum ionsarereducedto ions, solution,givingaluminum cryolite Aluminum oxidedissociatesinthe ions aremobileandablecar electrolyte For electrolysistooccur, the electrolysis Aluminum oxideisreducedby The filtered off. sodium hydroxidesolutionandare impurities remainundissolvedinthe Iron(III) oxideandtheother hydroxide solution,for mixed withanexcessofsodium alkalis oxide (itreactswithboth Aluminum oxideisan ( impurities, principallyiron(III)oxide aluminum Bauxite, the tetrahydroxoaluminate(III) solution. fluoride). aluminum fluorideandsodium molten solution ofaluminumoxideand charge. Theelectrolyteconsistsofa aluminum oxide. giving a where thesolutiondecomposes, Extraction Fe Manufacture 2 O filtrate, Al PATTERNS—METALS 3 ), thatmustberemovedbefore ). Aftergrinding,theoreis 3+ red intoaprecipitationtank, cryolite precipitate , and oxideions, must bemoltensothatthe in aHall-Héraultcell. is ore containing sodium obtained, contains 106 (a compoundof from which of puresolid precipitate ore filtrate electrolyte electrolysis amphoteric ming sodium acids O 2- ry electric ry . and Aluminum 2 1 (impure Al Seed crystals or Reactor carbon dioxide a e b f Extraction of pure aluminumoxide (Al decompose The electrolytic manufacture of aluminum Heater to Al(OH) Bauxite added c b a 3 2 (aluminum oxide dissolved incryolite) molten electrolyte solid crust of electrolyte graphite anodes O + 3 ) Solid Al(OH) Pure Al precipitate Al(OH) Grinder 2 O 3 NaOH solution 3 Addition of 3 g f e d insulation graphite liningto cell (cathode) tapping hole molten aluminum oxide 2 O 3 ) insoluble matter Fe Filter to remove obtain Al(OH) 2 O Filter to 3 and other – 3 d a c g 107

Iron: smelting PATTERNS—METALS

Key words 1 The blast furnace flux smelting iron ore, coke, and limestone ore reducing agent reduction slag hot gas outlet 1 The blast furnace ● Iron ores such as hematite and magnetite contain oxygen. To create pure iron, the ores are smelted in a blast furnace to remove the oxygen. ● A charge of iron ore, limestone, and coke is fed into the top of the furnace, and hot air is blown in toward the bottom through pipes called tuyeres. ● The coke is used as a fuel, as a 425°C reducing agent, and also to supply carbon, which dissolves in the molten iron formed. ● The limestone acts as a flux (cleaning 725°C agent), combining with acidic burning coke acts as a reducing agent impurities in the iron ore to form a liquid slag (the waste produce of smelting). ● Molten iron falls to the bottom of the furnace, where it is tapped. 1,225°C ● Molten slag floats on the molten iron and is drawn off. ● Hot gases (carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen, and unreacted oxygen) are removed at the top of the furnace. 1,725°C ● The conversion of iron oxide to iron is a reduction. The main reducing agent molten slag is carbon monoxide. ● Iron oxide is reduced to iron by hot air carbon monoxide, which itself is oxidized to carbon dioxide. molten iron ● The temperature inside the blast molten iron outlet furnace is sufficient to decompose limestone into calcium oxide and carbon dioxide. Calcium oxide then combines with impurities such as 2 Table of impurities of pig iron silicon dioxide to form slag. 2 Impurities Impurity % impurity in pig iron ● The iron that leaves the blast furnace (called pig iron) contains a variable Carbon 3 to 5 amount of impurities, including mation Ltd.

Silicon 1 to 2 carbon, silicon, sulfur, phosphorus, or and manganese. Sulfur 0.05 to 0.10 Visual Inf Phosphorus 0.05 to 1.5 Manganese 0.5 to 1.0 © Diagram

© Diagram Visual Information Ltd. ● ● ● 2 ● ● ● ● 1 slag alloy Key words furnace. and thesteelistappedfrom composition, theslagispoured off, steel hasreachedthecorrect aslag.Whenthe impurities forming added, andthesecombinewith Lime, fluorspar heat generatedmeltsthescrapsteel. scrap steelandtheelectrodes, between the is passed,anarcforms lowered intoposition.Whenacurrent the roofclosed,andelectrodes Scrap steelisplacedinthefur be raisedorloweredasrequired. through whichcarbonelectrodescan circular bathwithamoveableroof isa only coldscrapmetal.Thefurnace processuses The electricarcfurnace steel. this pointtomake differenttypesof metals andnon-metalsareaddedat separate reactionvessel.Additional amounts ofaluminumandsiliconina deoxidized byaddingcontrolled and notsuitableforcasting.Itis The resultingsteelishighlyoxidized a added duringtheoxygenblow, toform react withcalciumoxide,whichis monoxide, theremainingoxidesall With theexceptionofcarbon iron isalsooxidized. Impurities arereadilyoxidized.Molten vessel attwicethespeedofsound. purity oxygenisinjectedintothe andhigh lowered intothefurnace, lance, cooledbycirculatingwater, is Anoxygen iron fromablastfurnace. amounts ofsteelscrapandmolten ischargedwithcontrolled furnace In thebasicoxygenprocess, other metalsandnon-metals. Steel isan Basic oxygenprocess Electric arcfurnace slag. PATTERNS—METALS

alloy

, 108 and ironoreare of iron,carbon,and nace, The manufactureofsteel furnace door 2 Electric arc furnace 1 Basicoxygen process furnace swivel roof power cables hrigtecnetrPosition duringblowing Charging theconverter icagn h lgDischarging thesteel Discharging theslag pig iron (pipes) tuyeres water-cooled furnace roof tapping spout

a water-cooled panels aaa a graphite electrodes refractory lining refractory lining

a aa enters here compressed air

steel scrap

a a 109

Rusting PATTERNS—METALS

Key words 1 Rust experiment galvanizing Tube A Tube B Tube C hydroxide ion iron anhydrous magnesium oil calcium chloride rust

iron Rusting nail air ● Rusting is the result of a chemical cell being formed on the surface of iron boiled when it is in contact with water and water water oxygen from the air. No rust No rust Rust 1 Rust experiment ● The experiment at left proves that 2 Chemical process both water and oxygen are needed for rusting. dissolved oxygen air ● Tube A: When water is boiled, the air it contains is expelled, and oil prevents any air redissolving in the water. The nail is exposed to water but not Fe(OH) 2 water film oxygen and does not rust. Fe O .xH O 2 3 2 ● Tube B: Anhydrous calcium chloride 2+ – Fe 2OH +H O + 1O removes moisture from the air. The (rust) 2 2 2 nail is exposed to oxygen but not +2e– iron (or steel) water and does not rust. ● Tube C: The nail is exposed to both Fe 2e– water and oxygen, and rust forms on it.

anodic area cathodic area 2 Chemical process electron flow ● Iron atoms are oxidized to form first iron(II) ions, Fe2+, and then iron(III) 3+ ions, Fe , present in rust, Fe2O3.xH2O. 3 Rust prevention ● Oxygen is reduced and combined with water to form hydroxide ions, OH-. 3 Rust prevention ● Most methods of rust prevention involve stopping iron or, more commonly, steel from coming into contact with water and/or oxygen in air. These methods include painting, greasing, coating in plastic, coating in zinc (galvanizing), and coating in tin. ● Sacrificial protection involves bolting blocks of a more reactive metal, such magnesium blocks as magnesium, to a steel structure. The magnesium will oxidize more readily than the iron and will thus mation Ltd.

“sacrifice itself” in order to prevent or iron from rusting. Visual Inf © Diagram © Diagram Visual Information Ltd. ● ● ● ● 2 ● ● ● ● 1 slag electrolyte cathode anode Key words electro-refining. useful. refiningtobecommercially further It isporousandbrittlerequires than thecopper produced. circumstances maybemorevaluable platinum, andtin,insome cell. Thesemayincludegold,silver, electrolyte falltothebottomof the Impurities thatareinsolublein the Cu gradually becomeslarger: reduced tocopperatoms.Thecathode removed fromsolutionastheyare At thecathode,copperions are Cu(s) becomes smaller: solution. Theanodegradually oxidized tocopperionsandpassinto At theanode,copperatoms are sulfate solutionandsulfuricacid. electrolyte cathode copper anodeandasmallpure In electro-refining,alargeimpure impure copperiscastinto through ittoremoveanysulfur. The sulfur dioxide,andairisblown Blister copperismeltedtodriveoff copper Thisproductiscalled“blister form. to As theironcontentofmattefalls 4CuFeS chalcopyrite ( Copper sulfideores,suchas vir immiscible liquidslag, as muchcopperpossible,andan liquid sulfidephase(matte)containing Matte smeltingisusedtoproducea sand andblownintotheflashfurnace: Matte smelting Electro-refining 2Cu tually nocopper. 2+ about 1 percent, copper starts to about 1percent,copperstarts (aq) +2e at slag matte PATTERNS—METALS 2 ➞ S.FeS(l) +2FeSiO ” 2 (s) +5O and is98–99.5percentpure. are suspendedinan Cu consisting ofcopper(II) 2+ (aq) +2e CuFeS - ➞ 110 2 (g) +2SiO Cu(s) 2 ) are mixedwith - which contains 3 (l) +4SO anodes 2 (s) ➞ 2 for (g) converting Copper smeltingand oxygen sand andore anode copper impure 2 1 concentrate Matte smelting Electro-refining gas exit anode +– lgmatte slag silver, platinum, andtin) impurities (includinggold, cathode sand andore concentrate sulfuric acid sulfate and copper (II) solution of cathode copper oxygen matte pure slag 111

Reactions of copper PATTERNS—METALS

Key words hydrochloric acid sulfuric acid Cu2+ nitric acid transition metals oxidation state doubly ionized copper oxidizing agent

Dilute acids Reactions of copper ● Copper is a transition metal. Its normal oxidation state is copper(II), 2+ Concentrated nitric Dissolved Cu , but it also forms some copper(I), + or sulfuric acid H+ (aq) Cu , compounds. Copper is a relatively unreactive metal. It does not react with dilute strong acids, water, or CuO Cu O steam. 2 ● When heated in air at 800°C, copper is black copper red, insoluble Heat in air Heat in air oxidized to black copper(II) oxide: Cu oxide copper oxide 2Cu(s) + O (g) ➞ 2CuO(s) at 800°C above 1,000°C 2 At temperatures over 1,000°C, red copper(I) oxide is formed:

4Cu(s) + O2(g) ➞ 2Cu2O(s) Concentrated Both oxides react with dilute acids to hydrochloric form copper(II) salts. Air acid ● When heated in chlorine, copper (slow forms brown copper(II) chloride. ➞ tarnishing) Cu(s) + Cl2(g) CuCl2(s) ● White copper(I) chloride also exists and can be made by strongly heating Dilute copper(II) chloride: ➞ strong 2CuCl2(s) 2CuCl(s) + Cl2(g) acids It is also formed by the reaction of copper(II) oxide with concentrated hydrochloric acid via an complex ion, - [CuCl2] . When a solution containing this ion is poured into water, copper(I) chloride is precipitated. ● Copper tarnishes slowly in air, forming CuCO3.Cu(OH)2 CuCl basic copper(II) carbonate, a green patina white, compound of copper(II) carbonate, insoluble and copper(II) hydroxide, copper CuCO3.Cu(OH)2. It is this compound Heat chloride that produces the green coloration, in dry referred to as patina, on weathered chlorine copper. ● Copper reacts with both concentrated nitric and concentrated sulfuric acid. Both of these concentrated acids are powerful oxidizing agents and react with copper in a different way than a no reaction dilute acid reacts with a metal. Copper does not react with dilute acids. mation Ltd.

With concentrated sulfuric acid: or ➞ CuCl Cu(s) + 2H2SO4(l) 2 CuSO (aq) + 2H O(l) + SO (g) 4 2 2 Visual Inf brown copper chloride With concentrated nitric acid: Cu(s) + 4HNO3 ➞

Cu(NO3)2(aq) + 2H2O(l) + 2NO2(g) © Diagram © Diagram Visual Information Ltd. ● Valency ● Carbonates ● ● Hydroxides ● Oxides ● ● Reactivity hydroxide copper carbonate amphoteric aluminum Key words carbon dioxide,andwater. metalsalts, dilute acidstoforms gas. Thecarbonatesalsoreactwith oxide withthelossofcarbondioxide compounds. exhibit twooxidation statesintheir copper areboth transitionmetals state, table andexhibitsonlyone Aluminum isingroup3ofthe periodic heating tothecor copper(II) carbonatedecomposeon carbonates Aluminum andiron(III)donotform to givemetalsaltsandwater. All metalhydroxidesreactwithalkalis for hydroxide. Copper(II)hydroxide brown precipitateofiron(III) while iron(III)saltsproduceared- green precipitateofiron(II)hydroxide, salts. Iron(II)saltsproduceadir hydroxide solutiontosolutionsofits hydroxides bytheadditionofsodium two oxide, isamphoteric.Ironforms Aluminum salts andwater. oxides reactwithdiluteacidstoform is Aluminum hasone non-metals. All threemetalsreactdirectlywith metals. copper Aluminum solution ofacoppersalt. sodium hydroxideisaddedtoa has two: both acidsandalkalis. oxides: amphoteric ms asablueprecipitatewhen PATTERNS—METALS +3, initscompounds.Ironand is leastreactiveofthethree FeO Cu hydroxide . , 2 is O Iron(II) carbonateand Fe the mostreactiveand and thusreactswith and 2 112 O 3 responding metal , CuO oxide, and valency transition metals oxide oxidation state iron , lik Iron . Fe All metal e Al 3 aluminum O oxidation has three 2 4 O Copper . 3 , ty which and copper aluminum, iron,and Reaction summary: Change of valency Carbonate Hydroxide Oxide Reaction of elements Preparation Aluminum Change of valency Carbonate Hydroxide Oxide Change of valency Reaction of elements Carbonate Preparation Copper Hydroxide Oxide Reaction of elements Preparation Iron 4Al +3O 2Cu Fe Cu +2H Al Electrolysis of aluminumoxide Cu Thermal decomposition infurnace Fe Chemical reduction inblast furnace FeCl Al(OH) Al CuCO Unstable to heat. CuCO 2Cu +S 2Cu +O FeCO Unstable to heat. FeCO FeO +H Fe +H Fe +S→ 2Fe +3Cl 2Fe +2H Al 2Al +3H CuCl Only onoxidation Not formed Fe(OH) CuCl CuO +H Fe(OH) FeCl 2Fe AlCl Cu(OH) Fe +2HCl→ Cu +Cl 2Al +3Cl Al(OH) 2 2 3+ 2 2 2 O O O O 2+ (aq) S 2+ (aq) +3e 3 3 2 3 3 3 3 2 2 3 (s) +2NaOH(aq) air → 3 + + + + + + + + 2 +Cl + 3 3 3 2 +2l + SO 2 2 3NaOH → (s) +NaOH(aq) 3NaOH → 2NaOH 2 2 3H 2 3H 3CO → 2NaOH → H 2Cu +SO + 2 + + → 2 H 2 2 SO → + SO – 2 H SO 2 FeS SO → O 2 4 2 3HCl → 3HCl 2HCl → 2 SO → 2 → 2HCl 2 2(g) SO Cu (aq) – CuCl SO 4 SO → 4 SO + 4 2CuO 4 FeCl 2Al Al at cathode → Al → 4 2FeCl → 2 O 4 → →

FeSO 4 4 4 S → → → 2 2 → → 2Fe +3CO → → FeSO → CuSO → 2 2 → → Cl CuSO Al → 2 O 2Fe 2Cu 2 no reaction withdilute acid Al(OH) Fe(OH) Fe(OH) FeSO AlCl 6 FeCl FeCl Cu(OH) + 3 2 CuSO Al 3 CuCl Fe 4 (SO 2Fe(OH) oxide layer formed H 2 4 3+ (aq) + 2 + (aq) 4 (SO 4 (SO 2 → 3 3 + 3 2 3 H + → 4 4 + 2 → + +2Cl 4 ) → +l 2 3 H + + 3 2 + Na[Al(OH) 3 + SO 4 H 4 2 + 2Na[Al(OH) 2 3H 2 + ) + + FeO +CO + ) 3H 2H CO CuO +CO O 2 2H 3 + 3 2(s) 2 CO O 2 3NaCl 3NaCl 2NaCl 2 3H + + rust 2NaCl O 2 2 + 2 (aq) 2 – O O thenCu 2 O 3H 3H 2 + 2H + H 2 H 2 2 O O 2 4 O 2 2 O ](aq) O 2 4 with conc. acid ](aq) (amphoteric) + (aq) +l (aq) –

→ Cul (s) 113

The extraction of metals PATTERNS—METALS from their ores Key words electrolysis ore Metal (Date of discovery) Main ore from which Main method of reactivity series reduction Ranked from highest to it is obtained extraction lowest in reactivity series Extraction of metals ● The ease with which a metal is Sodium (1807) Rock salt Electrolysis of obtained from its ore is directly related Group 1 NaCl molten NaCl to its position in the reactivity series of metals. Electrolytic reduction Magnesium (1808) Magnesite Electrolysis of ● All of the group 1 and group 2 metals 2+ Group 2 MgCO3 and Mg molten MgCl2 and aluminum from group 3 are ions in seawater reactive metals and in the upper half of the reactivity series. They cannot be obtained from their ores by chemical Aluminum (1827) Bauxite Electrolysis of Al O reduction, i.e., by heating the ore with 2 3 a reducing agent such as carbon Group 3 Al2O3.2H2O in molten cryolite monoxide or carbon. These metals can (Na AIF ) only be obtained by electrolytic 3 6 reduction or electrolysis. ● Consequently, it was impossible to Zinc (1746) Zinc blende Heat sulfide in air ➞ obtain these metals before the discovery and development of Transition metal ZnS oxide. Dissolve oxide electricity at the end of the eighteenth in H SO , electrolyze century. All of these metals were first 2 4 made in the early years of the nineteenth century, several by English chemist Sir Humphrey Davy. Iron (ancient) Hematite Reduce Fe2O3 with

Transition metal Fe2O3 carbon monoxide Heating ● Zinc oxide and iron oxide are reduced by heating with carbon monoxide. Tin (ancient) Tinstone Reduce SnO2 with Although zinc can be obtained by Group 4 SnO carbon chemical reduction, approximately 80 2 percent of the world’s annual production is, in fact, obtained by Lead (ancient) Galena Heat sulfide in air ➞ electrolysis. ● All of the metals from iron and below Group 4 PbS oxide. Reduce oxide in the reactivity series are relatively with carbon easy to obtain from their ores by heating. ● Iron is obtained by reduction with Copper (ancient) Copper pyrites Controlled heating carbon monoxide ● Tin is obtained by reduction with Transition metal CuFeS2 with correct amount carbon (CuS + FeS) of air ➞ Cu + SO ● Lead is obtained by heating lead 2 mation Ltd.

sulfide in air to produce an oxide, or which is then reduced with carbon. ● Mercury (ancient) Cinnabar Heat in air ➞ Copper is obtained by controlled Visual Inf heating with the correct amount of air Transition metal HgS Hg + SO2 ● Mercury is obtained by heating in air. © Diagram © Diagram Visual Information Ltd. ● acid Reaction withdilute ● Reaction withsteam ● water Reaction withcold ● Reaction withoxygen ● Reactivity summary reactivity series reactivity oxide Key words dilute acids. below leaddonotreactwith decreasing vigor react withdiluteacids, All ofthemetalsdowntolead steam. below irondonotreactwith decreasing vigor. The metals to ironreactwithsteam water. Allofthemetals down with steamthancold Metals reactmorevigorously cold water. magnesium donotreactwith magnesium. Themetalsbelow decreasing vigordownto with coldwaterbut reactivity seriesreactreadily Metals atthetopof atmospheric oxygen. are notoxidizedby bottom ofthereactivityseries layer ofoxide. asurface butform not burn oxygen. Lessreactivemetalsdo in reactivity seriesreadilyburn Metals atthetopof star order oftheir in Metals canbearranged ftheirchemistr of metals isreflectedthroughall series. This iscalledthe ting withthemostreactive. PATTERNS—METALS The relativereactivityof reactivity Metals atthe 114 . y. reactivity The metals , dilute acid Reaction with steam Reaction with cold water Reaction with oxide shown /kJ mole of O metal reacts with1 Heat evolved when on heating Reaction withO 2 metals Reactivity summary: to form 2(g) displace H with excess O Na Na (e.g., Na peroxides of O of limited supplies (e.g.,Na form oxides K, decreasing vigor acid with from dilute K, decreasing vigor from steam with K, reactivity with decreasing from coldwater K K displace H displace H K 2 O explosively very violently violently 2 Na O 2 , but 2 2 O) in O 2(g) 2(g) 2(g) 2 ) Ca 2 832 723 Mg Fe,steadily Mg,very vigorous displace H displace H Al Al MgO Mg CaO Ca Fe decreasing vigor from steam with Mg reactivity with decreasing from coldwater Fe Fe ZnO Zn form oxides vigor to decreasing burn with 2 2 , O , O very slowly) very slowly lZn Al 3 3 2(g) 2(g) 1204 1272 1114 548 697 Fe HgO Hg CuO Cu PbO Pb H do not Pb, H do not layer ofoxide form asurface but only do not dilute acid cold water H do not 2(g) 2(g) 2(g) very slowly Pb from from steam from displace displace burn, displace Cu 436 182 Hg 311 on surface or oxidize do not burn H do not Au Au H do not H do not — Pt dilute acid cold water Ag Ag 2(g) 2(g) 2(g) 2 2 O O Ag from from steam from 3 displace displace displace Pt Au 54 61 — 115

Tests on metals: PATTERNS—METALS flame test Key words ion salt 1 Flame test solution

1 Flame test flame ● Several metal ions produce color characteristic colors when introduced to a bunsen flame either as a solid or as a solution of a salt. ● A clean platinum or nichrome wire is dipped in concentrated hydrochloric acid and then into the solid or platinum or nichrome wire solution. ● The sample is introduced to the sample middle of a non-luminous bunsen flame. 2 Flame coloration ● The following metals produce the following colors in the flame test: barium: apple green calcium: brick red copper: blue-green lithium: red potassium: lilac sodium: orange-yellow strontium: crimson 2 Table of flame coloration ● The lilac color of potassium is sometimes difficult to see and is better observed through blue glass that Color of flame Likely ion present Metal makes the flame appear purple. ● The orange-yellow color of sodium is Apple green Ba2+ barium very intense and may mask the color of other metal ions present. Blue-green Cu2+ copper

Brick red Ca2+ calcium

Crimson Sr2+ strontium

Lilac K+ potassium

Orange-yellow Na+ sodium

Red Li+ lithium mation Ltd. or Visual Inf © Diagram © Diagram Visual Information Ltd. ● ● ● 2 ● 1 sodium hydroxide salt precipitate hydroxide amphoteric Key words of insoluble hydroxides.Ifseveraldrops solutions. Allothermetalsform weakalkaline sufficiently toform are lesssolublebutstilldissolve solutions. Group2metalhydroxides and for Iron andcopperare sodium tetrahydroxoplumbate(II). Pb(OH) sodium tetrahydroxozincate(II) Zn(OH) sodium tetrahydroxoaluminate(III) Al(OH) initial whiteprecipitateisfor solutions ofsaltsthesemetals,an hydroxide solutionisaddedto are all Aluminum, zinc,andleadhydroxides themetal. used toidentify with sodiumhydroxidesolutioncanbe The reactionsofmetalsaltsolutions precipitate maynotbeseen. soluble andfor Group 1metal is addedtooquickly solution. Ifsodiumhydroxidesolution redissolve inexcess precipitatesthat some metalsform carr for a are addedtoasolutionofmetal soluble complexcompound. asolutionof dissolves, forming solution isadded,theprecipitate However solution. precipitates withsodiumhydroxide Producing thehydroxide The reactions precipitate Na Na Na[Al(OH) sodium hydroxide( med. Caremustbetaken when ying outthisreactionbecause 2 2 [Pb(OH) [Zn(OH) PATTERNS—METALS amphoteric 3 m 2 2 (s) +NaOH(aq)➞ (s) +2NaOH(aq)➞ (s) +2NaOH(aq)➞ , characteristic colored if excesssodiumhydroxide 4 ten gelatinous,is , ](aq) 4 4 of ](aq) ](aq) m strongalkaline hydroxides 116 . When sodium , theinitial sodium hydroxide transition metals transition metals NaOH are very ) med. solution salt, 2 metal hydroxides Tests onmetals: Lead nitrate Pb(NO Cu(NO Copper nitrate Fe(NO Iron(III) nitrate Fe(NO Iron(II) nitrate Zn(NO Zinc nitrate Al(NO Aluminum nitrate 1 The reactions Add asmallamount of NaOH Producing thehydroxide from themetallic salt to metal salt solution 3 3 3 3 3 3 ) ) ) ) ) ) 3 3 2 2 2 2 + + + + + + 3NaOH 3NaOH 2NaOH → 2NaOH 2NaOH 2NaOH → → white precipitate of zinchydroxide a → white precipitate of lead hydroxide → few drops of NaOH green precipitate of iron(II) hydroxide royal blueprecipitate of copper hydroxide → rust-brown precipitate of iron(III) hydroxide → → → → → → white precipitate of aluminumhydroxide metal salt 3NaNO 3NaNO 2NaNO 2NaNO 2NaNO 2NaNO solution 3 3 3 3 3 3 + + + + + + Al(OH) Fe(OH) Fe(OH) Zn(OH) Pb(OH) Cu(OH) A jelly-like solid forms 3 3 2 2 2 2 ↓ ↓ ↓ ↓ ↓ ↓ insoluble metal hydroxide 117

Tests on metals: PATTERNS—METALS metal ions Key words hydroxide reagent Reacations with reagents

● In addition to flame tests and the solution can be demonstrated by their properties of their hydroxides, reactions with particular reagents. the presence of some metal ions in

Metal ion in solutionTo the test solution Positive result

Alumnum Add 1 or 2 drops of litmus solution Blue lake – a gelatinous precipitate followed by dilute hydrochloric acid of aluminum hydroxide – is formed, until the mixture is just acidic. Then and this absorbs the litmus, leaving add ammonia solution until just the solution almost colorless. alkaline. Barium Add several drops of potassium A yellow precipitate of barium chromate solution. chromate. Lead ions also give a yellow precipitate, but lead chromate is deeper yellow and turns orange on heating. Copper Add ammonia solution drop by drop An initial blue precipitate of copper(II) until it is in excess. hydroxide that dissolves in excess ammonia solution to give a deep blue solution containing the complex ion 2+ [Cu(NH3)4] . Iron(II) Add several drops of potassium A deep blue solution is formed. hexacyanoferrate(III) solution.

Iron(III) Add several drops of ammonium Deep blood-red coloration. thiocyanate solution.

Lead Add several drops of potassium iodide A yellow precipitate of lead(II) iodide. solution.

Silver Add several drops of potassium A brick-red precipitate of silver chromate solution. chromate. mation Ltd.

Zinc Add ammonium chloride and A white, or more often dirty white, or ammonia solution, then pass hydrogen precipitate of zinc sulfide.

sulfide through the mixture. Visual Inf © Diagram © Diagram Visual Information Ltd. ● Lead ● Iron ● Zinc ● Aluminum ● Uses ofmetals galvanizing ductile copper aluminum alloy Key words join copperwiresandpipes. alloy ofleadandtin)iswidely used to water pipesandinpaints.Solder (an understood, leadwasalsoused for the past,beforeitstoxicnaturewas the manufactureofcarbatteries.In flashing onroofs.Itisalsousedasin imper Lead air. exposure towaterandoxygeninthe on with ironandsteelisthattheyrust and carbon).Theoneseriousproblem assteel(analloyofiron most often ofstructures, Iron isusedforallsorts preference totheiron. in iron andzinc,thezinccorrodes betweenthe electrolytic cellforms scratched, exposingtheiron,an Ifthegalvanizedironis from rusting. ontheironprotectsit zinc formed dipped inmoltenzinc,andthelayerof series. Zinc sof Aluminum alloys other metalsornon-metalstoform sometimes alteredbymixingitwith ofametalare The physicalproperties their physicalandchemicalproperties. The usesofmetalsarerelatedtoboth s of aluminumand frequently usedasduralumin(analloy of airplanes. tructural materialinthemanufacture tructural t formanyapplications.Itis is aboveiron has ahighdensityandis PATTERNS—METALS . vious towater, soitused as During has alowdensitybutistoo galvanizing, 118 copper in the zinc reactivity series lead iron ) reactivity as a iron is Uses ofmetals ● Copper ea s Reason Use Aluminum Metal Copper Lead Iron Zinc parts ofelectric cables.Copperdoesnot electricity andisusedfortheconducting drawn intowires.Itisagoodconductor of Copper isveryductile

and canbeeasily B A T T E R Y nickel) Coins (alloyed with Alloys (see above) Pipes Electric cables Solder (Pb/Sn alloy) Car batteries Roofing form of steel) all industries (inthe Structural material for bronze (Zn/Sn/Cu) brass (Zn/Cu) Alloys: steel Coating (galvanizing) Electric cables cookware s Structural material for hips, planes, cars, radiators. of heat.Itisusedforwaterpipes and react withwaterandisagood conductor corrode easily. Very ductile, does not Very good conductor. Low meltingpoint. possible. makes recharging Design of battery does not corrode. Very malleable and alloying. made suitable by properties can be Strong andcheap; elements. properties of theother Modifies the corrode easily. to iron; does not sacrificial protection Reactive —gives conductor. L corrosion. layer prevents Strong butlight; oxide ight, butgood 119

Reactivity of metals 1 CHEMICAL REACTIONS

Key words 1 Forming oxides and chlorides alkali hydroxide calcium magnesium chloride oxide copper sodium iron a 1 Forming oxides and chlorides ● Most metals react with air to form b metal oxides. Reactive metals like magnesium burn, producing light and heat. Less reactive metals like copper simply change color on heating: a oxygen or chlorine 2Mg(s) + O (g) ➞ 2MgO(s) b burning piece of reactive metal 2 2Cu(s) + O2 ➞ 2CuO(s) ● Metals will also form chlorides when 2 Forming hydroxides heated in chlorine: Mg(s) + Cl2(g) ➞ MgCl2(s) f Cu(s) + Cl2 ➞ CuCl2(s) 2 Forming hydroxides ● Very reactive metals like calcium and d sodium react with water to form solutions of metal hydroxides and hydrogen gas:

Ca(s) + 2H2O(l) ➞ Ca(OH)2(aq) + H2(g) 2Na(s) + 2H2O(l) ➞ e 2NaOH(aq) + H (g) c 2 ● Calcium hydroxide is less soluble in c calcium water and forms a weak alkali. d cold water ● e inverted filter funnel Sodium hydroxide is very soluble in f hydrogen water and forms a strong alkali. 3 Less reactive metals 3 Less reactive metals ● Less reactive metals, which react with j k water very slowly or not at all, react with steam to form metal oxides and i hydrogen gas. h ● Magnesium reacts very slowly with water but readily with steam:

Mg(s) + H2O(g) ➞ MgO(s) + H2(g) ● Iron does not react with water but l reacts with steam to form iron(II) diiron(III) oxide:

3Fe(s) + 4H2O(g) ➞ Fe3O4(s) + 4H2(g) ● g The least reactive metals, such as copper, do not react with water or steam. g water mation Ltd. or h safety tube i steam

j magnesium ribbon Visual Inf l k hydrogen ignites lheat © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● current 2 ● ● ● 1 oxide limewater cathode carbonate anode Key words electrical cellisfor MgCO stream ofhydrogengas. be reducedbyheatingthemina CuCO copper atoms. while copperionsarereduced to Zinc atomsareoxidizedtozinc ions, Cu occurs atthecathode: sulfate solution,adifferentreaction porous vesselcontainingcopper(II) by a If thecopperrodissurrounded 2H hydrogen gas: Hydrogen ionsarereducedto electrode (cathode The copperrodbecomesthenegative Zn(s) atoms areoxidizedtofor electrode (anode) The zincrodbecomesthepositive flows. connected externally, electriccurrent the twometals.Ifmetalsare potential voltagedifferencebetween placed indilute When rodsofzincandcopperare turns tube intoanother. Carbondioxide air andcanbepouredfromonetest Carbon dioxidegasismoredensethan Li All group1metal the The carbon dioxidegas: themetaloxideand heating, forming metal carbonatesdecomposeon decomposed onheating.Allother exception oflithiumcarbonate,arenot Metal compounds Generating electric 2 2+ CO + (aq) +2e reactivity series CHEMICAL REACTIONS oxides (aq) +2e 3 3 limewater ➞ 3 (s) (s) (s) Zn ➞ ➞ ➞ 2+ of metalsthatarelowin CuO(s) +CO Li MgO(s) +CO - (aq) +2e - ➞ 2 120 ➞ O(s) +CO sulfuric acid milky. H carbonates Cu(s) 2 med, andthereisa of thecell.Zinc ) (g) e copper, can , sulfuric acid reactivity series of thecell. lik - m zincions: 2 2 2 (g) (g) (g) simple a , , with the Reactivity ofmetals2 2 Reduction of oxides 1 v u t s g f e d c b a r Method 2 q p k copper sulfate solution dilute sulfuricacid porous vessel zinc rod copper rod heat hydrogen ignited moisture collects here porcelain vessel metallic oxide slope downward combustion tube clampedto hydrogen Reactions of metal compounds Generation of electriccurrent by mechanical reaction a m b r n o l h c g g q p o n m l k Method 1:simplecell dilute sulfuricacid beaker copper rod connecting wire electron transfer electric bulb zinc rod d i e Effect of heat oncarbonate j i h limewater carbon dioxide metallic carbonate f j u s v t 121

Electrolysis CHEMICAL REACTIONS

Key words 1 Electrolysis: schematic 2 Electrolysis of salt solutions anion electrolysis a anode electrolyte cathode b cation electrode

1 Electrolysis ● Electrolysis is the process by which an electrolyte (a substance that conducts electricity) is decomposed when a direct current is passed through it between electrodes. Positive cations i move to the cathode to gain electrons; c negative anions move to the anode to h h lose electrons. ● d e Substances are either deposited or liberated at the electrodes depending on the nature of the electrodes and electrolyte. f g g 2 Salt solutions ● Two electrolytes undergo electrolysis at the same time when they are 3 Electrolysis of water 4 U tube connected in a circuit by a salt bridge. ● The platinum electrode in the left- +–hand beaker is the anode and attracts negative ions, which are oxidized. ● The platinum electrode in the right- hand beaker is the cathode and attracts positive ions, which are reduced. l m 3 Water ● The electrolysis of water yields o q n hydrogen at the cathode and oxygen at the anode. Hydrogen and oxygen n are formed in the ratio of 2:1. 4 U tube j k ● The ions present in dilute sulfuric acid + - 2- – + are H , OH , and SO4 . Hydroxide ions are discharged at the anode, leaving a surplus of hydrogen ions, so the electrolyte in the left side of the U tube becomes increasingly acidic. p ● The ions present in sodium sulfate + + - 2- solution are H , Na , OH , and SO4 . a battery j platinum cathode Hydrogen ions are discharged at the b electric bulb k platinum anode cathode, leaving a surplus of c liquid under test l hydrogen mation Ltd. d poly(ethene) support m oxygen hydroxide ions, so the electrolyte in or e copper plates n water acidified with dilute sulfuric acid the right side of the U tube becomes f glass vessel o dilute sulfuric acid

increasingly alkaline. Visual Inf g platinum electrodes p agar jelly colored pink by phenolphthalein h electrolyte solution in beakers and alkali i salt bridge q sodium sulfate solution © Diagram © Diagram Visual Information Ltd. ● ● ● 4 ● ● ● 3 ● ● 2 ● ● 1 ● ● concentration Electrode activityand inert electrolysis electrode cathode anode Key words the reaction. bigger. is deposited,andthecathodegrows Reaction atthecathode:coppermetal anode growssmaller. into solutionascopperions,andthe Reaction attheanode:coppergoes (active) electrodes. undergoes electrolysisusingcopper electrodes whencopper(II)sulfate The followingreactionsoccuratthe is depositedonthecathode. Reaction atthecathode:coppermetal produced Reaction attheanode:oxygenis electrodes. (inert) undergoes electrolysisusingcarbon electrodes whencopper(II)sulfate The followingreactionsoccuratthe produced Reaction atthecathode:hydrogen produced Reaction attheanode:chlorine produced Reaction atthecathode produced Reaction attheanode: reaction; activeelectrodestak Inert solution andtypeof depending ontheconcentrationof The resultsof Dilute solution Inert electrodes Concentrated solution Active electrodes CHEMICAL REACTIONS electrodes takeinthe nopart electrolysis 122 electrodes oxygen : hydrogen differ e part in e part used. activity andconcentration Electrolysis: electrode 3 4 sodium chloride 1 Dilute solution Inert electrodes Active electrodes +– +– +– solution copper (II)sulfate solution copper (II)sulfate chloride solution dilute sodium electrodes electrodes electrodes copper carbon carbon sodium chloride 2 Concentrated solution +– +– +– solution copper (II)sulfate solution copper (II)sulfate chloride solution concentrated sodium electrodes deposited electrodes electrodes copper copper carbon carbon 123

Acids: reactions CHEMICAL REACTIONS

Key words 1 Main reactions of an acid acid oxidation base oxide salt + carbonate carbonate salt acid CO 2 catalyst + H2O hydroxide

1 Main reactions of an acid metal ● Dilute acids react with all metal base carbonates to give a metal salt, carbon dioxide, and water. ● Dilute acids react with bases to give salts plus water. salt ● Dilute acids react with most metals to salt + H2O give a metal salt and hydrogen. + H2 ● Dilute acids are neutralized by metal oxides and metal hydroxides to form a metal salt and water. 2 Examples of reaction type 2 Example of reaction type Acid with carbonate Na CO (s) + 2HNO (aq) ➞ 2 3 3 ● Sodium carbonate reacts with dilute 2NaNO (aq) + CO (g) + H O(l) 3 2 2 nitric acid to give sodium nitrate, carbon dioxide, and water. ● Hydrochloric acid reacts with sodium Acid with base HCl(aq) + NaOH(s) ➞ NaCl(s) + H2O(l) hydroxide to form a salt and water. ● Zinc reacts with dilute hydrochloric acid to give zinc chloride and Acid with metal Zn(s) + 2HCl(aq) ➞ ZnCl2(aq) + H2(g) hydrogen. ● Copper(II) oxide reacts with dilute sulfuric acid to give copper(II) sulfate and water. Acid neutralized CuO(s) + H2SO4(aq) ➞ CuSO4(aq) + H2O(l) by oxide 3 Sulfur trioxide ● Sulfur trioxide is a white crystalline solid obtained by oxidation of sulfur 3 Laboratory preparation of sulfur trioxide dioxide. It dissolves in water with a hissing noise and the production of c d heat, forming sulfuric acid. Sulfur trioxide is employed as a dehydrating a agent. ● Sulfur trioxide is made in the laboratory by passing a mixture of dry sulfur dioxide and dry oxygen over a heated platinum catalyst. Sulfur trioxide melts at 17°C and condenses as a solid in a suitably cooled beaker. b g ● Industrially it is made using the f contact process (see pages 75 & 76).

a oxygen b dry SO

2 mation Ltd.

c plantinized asbestos as a catalyst or d combustion tube e e crushed ice and salt Visual Inf f white smoke of SO3 g heat © Diagram © Diagram Visual Information Ltd. ● ● of HNO 4 ● ● 3 ● ● 2 collected bydownwarddelivery. The gasismoredensethanairand ● 1 soluble nitric acid hydrogen hydrochloric acid Key words over aheatedplatinum catalyst. laborator This processcanbemodeledin the dioxide andwater. dioxide gas,reactionofnitrogen oxidation ofnitrogenoxideto nitrogen production ofnitrogenoxidegas, involving threestages(seepage76): oxidation ofammoniainaprocess Nitric acidismadeindustriallybythe decompositionoftheacid: thermal bythe of nitrogendioxide,formed nor The productofthisreactionis nitrate withconcentrated reaction ofsolidsodiumorpotassium Nitric acid prevents suckback. sur positioned sothelipisjustunder funnel passing itintoaninverted The gasisdissolvedinwaterby reaction vessel. would besuck directly intowaterbecausethe thegas tubecarrying placing adelivery acid soluble Hydrogen chlorideisextremely concentrated sulfuricacid: reaction ofsodiumchlorideand Hydrogen chloride 4HNO KNO 2NaCl(s) +H Preparing HClgas Preparing nitricacid Preparing HClacid chloride Industrial preparation 4NO Na KHSO aeo h ae.Thefunnel face ofthewater. mally yellowduetothepresence 2 CHEMICAL REACTIONS . 3 SO (s) +H It cannotbedissolvedsimplyby 2 3 (g) +2H (l) 4 in water 4 (aq) +HNO (aq) +2HCl(g) y 3 ➞ by passingammonia vapor can bemadebythe 2 2 SO SO ed backintothe 124 2 , O(g) +O 4 4 forming forming (aq) (aq) gas ismadebythe 3 sulfuric acid ➞ ➞ 2 hydrochloric sulfuric acid (g) : Preparation ofacids d c b 3 4 a chloride (gas) 1 i a b heat HCl gas collected concentrated sulfuricacid rock salt Preparation of hydrogen Laboratory preparation of nitricacid Industrial preparationofnitricacid h d l m h n j q c hydrochloric acid 2 g f e HCl acid) water (to become dilute filter funnel HCl filter g Preparation of f o k p k j i h q p o n m l pure nitricacid water jacket sulfuric acid plus concentrated solid sodium nitrate heat litmus goes red brown gas through apparatus pump sucksgases platinized asbestos combustion tube with water (50%) ammonia diluted concentrated e 125

Bases: reactions CHEMICAL REACTIONS

Key words 1 General reactions of a base with an acid acid salt + + base universal carbonate indicator acid metal salt water hydroxide oxide oxide + + Bases acid metal salt water hydroxide ● A base is a compound that reacts with an acid to form a salt. Common bases + ++ are metal oxides, metal hydroxides, and metal carbonates. acid metal salt water CO2 carbonate 1 General reactions with acids 2 Metal oxide and acid ● Metal oxides react with acids to form salts and water. ● Metal hydroxides also react with acids to form salts and water. ● Metal carbonates react with acids to form salts, water, and carbon dioxide. 2 Metal oxide and acid ● The reaction of magnesium oxide (MgO) with hydrochloric acid (HCl) can be followed by adding a few drops of universal indicator to the acid. ● Initially the indicator is red. When magnesium oxide is added to the reaction, the following reaction occurs: MgO(s) + 2HCl(aq) ➞ MgCl2(aq) + H2O(l) ● When there are equivalent amounts of heat is applied magnesium oxide and hydrochloric Magnesium oxide is added to hydrochloric Neutral solution, indicator is green acid, the indicator turns green, acid and indicator signifying all of the acid has reacted and the mixture is neutral.

3 Carbonate and acid 3 Carbonate and acid ● The reaction of magnesium carbonate

(MgCO3) with hydrochloric acid (HCl) can be followed by observing the carbon dioxide gas evolved. ● Initially bubbles of gas are evolved as the following reaction occurs: MgCO3(s) + 2HCl(aq) ➞ MgCl2(aq) + H2O(l) + CO2(g) ● When all of the hydrochloric acid has gas reacted, no gas is produced, and bubble excess insoluble magnesium carbonate remains in the beaker. mation Ltd. or Visual Inf Cabonate is added to hydrochloric Neutral solution, indicator is green acid and indicator © Diagram © Diagram Visual Information Ltd. ● ● ● 2 ● ● ● ● 1 neutral insoluble indicator base acid Key words sodium hydroxide. chloride fromhydrochloricacidand cool. allowing theremaining solutionto the copper(II)sulfatesolution and boilingoffsomeofthewaterfrom by areobtained Copper(II) sulfatecrystals sulfate. leaving abluesolutionofcopper(II) remains. Theexcessisfilteredoff, has reactedandnoacidresidue to ensurethatallofthesulfuricacid An excessofcopper(II)oxideisused Salts aremadefrom cool. allowing theremainingsolutionto the sodiumchloridesolutionand boilingoffsomeofthewaterfrom by areobtained Sodium chloridecrystals hydroxide solutionbutnoindicator. hydrochloric acidandsodium exactly thesamevolumesof procedure mustberepeatedusing to thepresenceofindicator sodium chloride,whichisimpuredue The flaskcontainsasolutionof the reactionmixtureis the indicatorchanges,showingthat intotheflaskuntilcolorof is run hydroxide solution.Hydrochloricacid indicator conical flask.Afewdropsofasuitable hydroxide solutionisplacedina acid, andaknownvolumeofsodium The buretteisfilledwithhydrochloric acids Titration oxide andsulfuricacid. bythereactionofcopper(II) formed can becalculated. addition sothevolumeofacidneeded acid. F adding anexcessofthebaseto burette isnotedbeforeandaf volume ofhydrochloricacidinthe From asolublebase From aninsolublebase CHEMICAL REACTIONS and or example,copper(II)sulfateis is usedtomake are addedtothesodium soluble bases, 126 titration soluble salt insoluble neutral. e.g., sodium salts ter bases by from . The The d c b a Bases: formingpuresalts Example: copperoxideandsulfuricacid 2 Example: sodiumchloridefromhydroxideandhydrochloricacid 1 out the procedure volume of acidintheburette before carrying colorless. Add theaciduntil thesolution just turns alkali andphenolphthalein indicator acid burette b dilute acid Add the base to From asoluble base (alkali) From aninsoluble base as shown apparatus Set upthe h a c neutralization (e–d) of acidneeded for Measure thevolume d more willdissolve the base until no Warm gently, adding j i 25 20 15 10 5 0 h 25 20 15 10 5 0 e j i h g f e (i.e., e–d) measured above amount of acid indicator, addingthe but withoutusingthe Repeat theprocedure, excess solid neutralized acid heat boiling water salt solution has turned colorless volume of acidremaining whentheindicator the filtrate solid andcollect Filter off excess Evaporate off filtrate excess water excess Evaporate off f h h g 127

Proton transfer: CHEMICAL REACTIONS neutralization of alkalis Key words ammonium proton hydroxide species 1 Water particles ammonium ion hydronium ion hydroxide ion H H H 1 Water particles O H O ● In a water molecule, the oxygen atom H O forms bonds with two hydrogen H atoms. The oxygen atom and the hydrogen atom each donate one Neutral water molecule Hydronium ion: Hydroxide ion: electron to the bond. The oxygen protonated water deprotonated water atom also has two pairs of non- molecule molecule bonding electrons, which can be donated to form bonds with other species. ● In acidic solutions, each proton reacts 2 Ammonia solution turns universal indicator blue with a water molecule to form a hydronium ion.A pair of non-bonding H electrons forms the new H-O bond: + + H H H + H2O ➞ H3O ● An hydroxide ion is formed by the loss N of a proton from a water molecule: O + - H2OH + OH HH 2 Ammonium ions

● The ammonia molecule, NH3, has a similar structure to the water Ammonia molecule has To show the extra- H O an extra proton electron in the molecule, 2 , in the sense that the H H hydroxide ion nitrogen atom has a pair of non- bonding electrons that it can donate to N form a bond with another species. H ● Ammonia reacts with the protons in an acid to form the ammonium ions: + + H NH3 + H ➞ NH4 ● The four N-H bonds in the ammonium H O ion are directed toward the corners of a tetrahedron, giving a similar structure to methane. This keeps the bonding pairs of electrons as far away To show the attraction between the molecules and the breaking of the from each other as possible. bond in the molecule 3 Schematic of proton transfer 3 Schematic of proton transfer in diagram 2 ● Ammonia is very soluble in water and dissolves to form a weak alkaline H H H H solution that is sometimes referred to as ammonium hydroxide: + - NH3 + H2O NH4OH NH4 + OH H N H O HON H ● mation Ltd. Ammonia solution contains or + ammonium ions, NH4 , and hydroxide OH- H H ions, , and has similar reactions to Visual Inf solutions of soluble metal hydroxides, molecules ions such as sodium hydroxide. © Diagram © Diagram Visual Information Ltd. ● ● ● 4 ● 3 ● 2 ● ● MgO 1 ● Neutralizing bases lattice hydronium ion base acid Key words oxide a Sulfuric acid MgO(s) +H Nitric acid MgO(s) +2HNO Hydrochloric acid MgO(s) +2HCl(aq)➞ used. nature ofthesaltdependsonacid The of amagnesiumsaltisformed. The acidisneutralized,andasolution solution. down, releasingmagnesiumionsinto The magnesiumoxidelatticebreaks of amolecule to theoxideion,forming Each hydroniumiontransfersa 2H oppositely chargedhydroniumions: are donatedtofor Twooxygen atom. pairsofelectrons electrons intheouterorbitalof In anoxideion,thereareeight attracted toeachother. these oppositelychargedionsare magnesium oxideisaddedtoanacid, negative charge.Whensolid charge, whileoxideionscarr apositive Hydronium ionscarry H An acidcontains lattice Magnesium oxide Metallic Transfer Attractions Neutral solution 3 salt MgSO MgCl Mg(NO magnesium chloride O water 3 O + CHEMICAL REACTIONS . + plus water. ions, 2 of magnesiumions, O + 4 (aq) +H . bases in acid (aq) +H 3 ) 2- 2 ➞ (aq) +H 2 O SO ➞ ➞ 2- magnesium nitrate neutralize . 128 4 3H magnesium sulfate 3 2 (aq) (aq) hydronium ions 2 O(l) O(l) 2 m ➞ consists ofaregular O 2 salt proton oxide magnesium oxide bonds with O(l) ➞ ➞ acids Mg a y 2+ to form proton , and , neutralization ofbases Proton transfer: oxide lattice magnesium ion hydronium molecule water solid anddilute acid 1 place 3 Mg Mg Magnesium oxide (MgO) Proton transfer takes 2+ 2+ H H O + O O O + 2– H H 2– H H Mg Mg H 2+ 2+ H H O + + O H H O O 2– 2– H hydronium ions 2 oxide lattice hasdissolved produced of and part the 4 Mg Mg The oxide ionsattract the A H 2+ 2+ neutral solution is O H H H H O O 2– O + H H Mg Mg + H 2+ 2+ O H H O H O O 2– 2– H 129

Proton transfer: CHEMICAL REACTIONS metallic carbonates Key words carbonate orbital carbonic acid salt 1 Carbonate ions attract 2 Hydrogen carbonate hydronium ion hydronium ions molecules and water molecules are produced Metallic carbonates ● Metallic carbonates neutralize acids to form a metal salt, carbon dioxide, and water. water molecule 1 Attraction ● Group 1 metal carbonates are soluble in water and can be used as solids or HHHH in solution. Other metal carbonates H H H H O O are insoluble in water and are used as O O solids. proton ● All metal carbonates contain the transfer 2- H H carbonate ion, CO3 . All acids contain + HH the hydronium ion, H3O . ● Hydronium ions carry a positive charge, while carbonate ions carry a O– O– OO negative charge. When a carbonate is C C added to an acid, these oppositely charged ions are attracted to each carbonate 2– other. ion (CO ) ● O 3 O In a carbonate ion, each of the three oxygen atoms has eight electrons in its outer orbital.A pair of electrons is donated from two of the oxygen atoms to form bonds with oppositely charged hydronium ions. 3 A hydrogen carbonate 4 A carbon dioxide molecule molecule splits and water molecule are 2 H2CO3 and water produced ● The result is the formation of carbonic acid, H2CO3, and water: 2H O+ + CO2- ➞ H CO + 2H O H H 3 3 2 3 2

3 H2CO3 splits O ● Carbonic acid is a weak acid that only exists in solution. It readily breaks O H down to carbon dioxide and water: H2CO3 H2O + CO2

O 4 CO2 and water O C ● In an acid–carbonate reaction, some of the carbon dioxide will remain in solution, but most will be given off as C bubbles of gas. O H ● The gas can be identified by bubbling it into limewater. Carbon dioxide turns mation Ltd.

limewater milky due to the formation or O of insoluble calcium carbonate.

● The acid is neutralized by the Visual Inf carbonate, and a salt is formed. The nature of the salt depends on the metal carbonate and the acid used. © Diagram © Diagram Visual Information Ltd. ● ● ● ● schematic 4 & 3 ● ● ● 2 ● ● ● 1 ● Neutralizing acids covalent bond ammonia Key words for bond in water When hydrogen chlorideisdissolved hydronium ion and achlorideion. a atom andahydrogenatom,forming covalent bondbetweentheoxygen oxygen atomisdonatedtocreate a A H water, anacidicsolution isformed: When hydrogenchloridedissolvesin molecules. compound andexistsasdiatomic Hydrogen chloridegasisacovalent electrons. electrons andonepairloneof electrons: threepairsofbonding byeight nitrogen atomissurrounded In anammoniamolecule,each lone pairsofelectrons. pairs ofbondingelectronsandtwo byeightelectrons:two is surrounded In awatermolecule,eachoxygenatom bonding electrons(lonepairs). electrons andthreepairsofnon- electrons: onepairofbonding byeight chlorine atomissurrounded In ahydrogenchloridemolecule,each nitrogen atomfor its outerorbit.In A molecule the with twohydrogenatoms,forming covalentbonds the oxygenatomforms outer orbit.Inhydrogenoxide(water), An oxygenatomhassixelectronsinits the chlorineatomfor its outerorbit.In A salt andwater. Bases reactwithacidstoproducea the molecule with threehydrogenatoms,for Molecules Schematic 2 lone pairofelectronsfroman nitrogen atomhasfiveelectronsin chlorine atomhassevenelectronsin + O ming themolecule CHEMICAL REACTIONS with onehydrogenatom, HCl Proton transferand , it forms an ioniccompound. it forms H ➞ 2 O H NH . 130 3 O 3 + ammonia, hydrogen chloride . ms covalentbonds + hydrogen ms acovalent Cl chloride HCl - . the ming , neutralization ofacids Proton transfer: pairs lone 1 3 2 4 H molecule Hydrogen chloride Examples of molecules Proton transfer Schematic of themolecules shown indiagram1 lone pairs Schematic of proton transfer H H molecule Hydrogen chloride Attraction begins Cl H Cl O H O H H Cl p lone H airs l one pairs H H Cl H Water molecule ae oeueAmmoniamolecule Water molecule The bondbreaks O O H O H lone pairs H Cl H H H one extra proton A chlorine atom with O HH H Ammonia molecule is complete Transfer of theproton A water molecule with H HH H one extra proton N H lone pairs O Cl H N Cl H 131

Collision theory CHEMICAL REACTIONS

Key words 1 Collision theory activation energy effective collision AAproduct reactant B B

No collision between the particles of the reactants: no reaction 1 Collision theory ● Reactions occur when particles collide with sufficient force to provide the energy needed to start a reaction. ABB A ● If particles collide with insufficient force to start a reaction, they simply bounce off each other. Weak collision: no reaction ● A collision that brings about a reaction is called an effective collision .Particles of reactant collide, and particles of product are formed: A + B ➞ C + D ADB C reactants products ● Not every collision between particles gives rise to a reaction, but every set of Effective collision: reaction particles that do react have to collide. 2 Maxwell-Boltzman distribution 2 Maxwell-Boltzman distribution ● Because all the particles of a particular chemical, element, or compound have the same mass, the energy of the particles is directly related to their speed. ● In any mixture of moving particles, the energy at which an individual particle is moving will vary.

) ● The Maxwell-Boltzman distribution E (

y shows how the number of particles in g r

e a sample is distributed at different n

e energies at a particular temperature. h t i ● There are no particles at zero energy. w

s There are relatively few particles at e l c

i very high energy, but there is no t r

a maximum energy value. p

f ●

o In order to react, particles need to r

e have a minimum amount of energy, b

m called activation energy. The u

N activation energy is marked on the graph by a line, parallel to the Y axis, at a point on the X axis that

symbolizes the activation energy (EA). mation Ltd. or Visual Inf EA Kinetic energy © Diagram © Diagram Visual Information Ltd. ● 4 ● ● 3 ● ● 2 ● ● 1 ● Surface area surface area reactant immiscible diffusion Key words place. greater the of reactant,thesmallerobjects, chemical reactioncanoccur with eachother can onlytak immiscible one agas,orifthetworeactants are If oneofthereactantsisaliquid and more quickly. of reactantsspeedstheprocess Stirring diffusion together, theywilleventually mixby areadded When reactantparticles lumps). used ratherthangranulatedzinc(large quickly ifzincdust(finepowder)is This reactionproceedsmuchmore hydrogen gas: zincchlorideand acid toform Zinc reactswithdilutehydrochloric areaof surface A ofthesolid. the surface The reactioncanonlytake placeon the In orderforareactiontotake place, take place. thefaster thereactionwill interface, areaofthe The largerthesurface to collide. fortheparticles maximum opportunity easy forthemtomix,givingthe the reactantsaregasesorliquids,itis now becomes area with sides1cm,thetotalsurface the samecubeisdividedinto8cubes Zn +2HCl➞ Total surfacearea Mixing Reduced surfacearea Interface surfacearea cube withsides2cmhasatotal mixing sothereactiontakes place reactants CHEMICAL REACTIONS , and areactionwilltak surface area surface liquids, thenthereaction e placeattheinterface. ZnCl must comeintocontact 8cm 48 = 8 x 6 x 1 x 1 = 6 x 2 x 2 132 . Thus,foragivenmass 2 H + 2 on whichthe 24 cm . Ifallof e 2 If . 2 . surface areaandmixing Rates ofreaction: 1 4 3 2 Total sufacearea Mixing Reduced surfaceareareaction Interface surfacearea B A A B 2cm A B B A A B interface 2cm 2cm A small B A zinc dust B diffusion stirring rapid slow 1cm 1cm 1cm A A B B B A B A granulated A A interface B zinc large A B B 133

Rates of reaction: CHEMICAL REACTIONS temperature and Key words activation energy product concentration reactant

1 Temperature (distribution of molecular energies at T1 and T2) 1 Temperature ● Temperature is an important factor in determining rate of reaction.

y ● T1 When temperature increases, the g r

e average speed of the particles in a n e substance increases. The graph n e

v shows the Maxwell-Boltzman i

g T 2 distribution at two temperatures, T2 a

g is greater than T1. n i

v ●

a The number of particles is constant, so h

s the area under the two curves is the e l c

i same. However, the average energy of t r T a the particles at 2 is greater. The area p

f of the curve to the right of the o

r E e activation energy line ( A) is greater b T m for 2. Therefore, at this temperature a u

N higher proportion of particles have sufficient energy to react. 2 Concentration ● An increase in the concentration of a

EA chemical, or the pressure of a gas, Kinetic energy means that there will be more particles within a given space, so particles will collide more often. 2 Concentration 3 Rate of reaction ● The rate of any reaction is the speed at which the reactants are converted to A B A A A B products. This can be qualified as the A B B A change of concentration of reactants B or products. A A B ● Changes in concentration can be B A A B measured by: A B A B A B 1. appearance or disappearance of color in reactants or products A A A B A B 2. volume of gas evolved A 3. changes in pH B A B B 4. heat produced A B B B A B A 5. changes in pressure.

Low concentration High concentration mation Ltd. 3 Rate of reaction or

Change in concentration Visual Inf Rate of reaction = Time © Diagram © Diagram Visual Information Ltd. ● ● ● ● ● ● Concentration overtime rate ofreaction concentration Key words seconds (s)is0.0035moldm 300 concentration ofbromineafter time andthegradientmeasured.The concentration = concentration changes. of therateatwhichbromine the reactioncanbeexpressedinter falls duringthereaction,sorateof mol dm cur at anygiventime,atangenttothe In ordertoobtaintherateofreaction positive value. necessary negative signintheexpressionis bromine isbeingusedup.The concentration isnegativebecausethe The rateofchangebromine - - The The concentrationofbromine, relating thistothe and brown atdifferenttimeintervals measuring theintensityofred- The reactioncanbefollowedby Br The reactioniscatalyzedbyacid: according tothefollowingequation. methanoic acidinaqueoussolution Bromine reactswithanexcessof rate ofreactionatthistimeis1.2x10 bromine. rate ofchangebromine d[Br 2Br 2 (aq) +HCOOH(aq)➞ ve mustbedrawnatthatpar dt CHEMICAL REACTIONS rate ofreaction - 2 (aq) +2H ] -3 s to givetherateofreactiona -1 . 134 + (aq) +CO concentration = H + 2 (g) -3 . [Br The ticular of 2 ] ms , -5 concentration overtime Rates ofreaction: Gra –3 between me [Br2] mole dm ph to show thevar 0.008 0.004 0.009 0.006 0.005 0.002 0.003 0.007 0.001 0.010 0 0 than oic aci 100 iat d ion of bromine co and bromine 03 200 Tim 0 nce 0 0 6 500 400 0 e (s ntrat econ ion ds) with timeinth time =3 Ta nge nt at 0 0s e re 0 action 0 700 135

Rate of reaction vs. CHEMICAL REACTIONS concentration Key words concentration rate of reaction Graph to show the variation of reaction rate with bromine concentration

3.0

Rate vs. concentration ● In order to draw a graph showing how 2.7 the rate of reaction varies with bromine concentration, it is necessary to find the rate of reaction at different times and, therefore, different bromine concentrations. 2.4 ● The graph shows that the rate of reaction is directly proportional to the bromine concentration. Reaction rate ϰ[Br2], therefore, Rate of reaction = k[Br2] where k is a 2.1 constant, known as the rate constant or the velocity constant for the reaction. ● This reaction is said to be first rate with respect to bromine since 1.8 1 doubling the concentration of bromine – s

3 doubles the rate of the reaction. –

m ● Since rate of reaction = k[Br ], then to

d 2 e l find the units of k: o

m k = rate of reaction =

/ 1.5 5 [Br2] 0 1 mol dm-3 s-1 = s-1 × t ] mol dm-3 2 d r

B k [ The unit of the rate constant, , for d -1 – first order reactions is s . 1.2

0.9

0.6

0.3 mation Ltd. or Visual Inf 0 0 0.0010.002 0.003 0.004 0.005 0.006 0.007 0.008

–3 [Br2] / mole dm © Diagram © Diagram Visual Information Ltd. ● ● ● 2 ● ● ● ● 1 reactant rate ofreaction product concentration Key words rate =k[reactant] reactant. Therateequationis: be reaction, thenthereactionissaid to therateofa reactant quadruples If rate =k[reactant] rate equationis: order withrespecttothereactant.The then thereactionissaidtobefirst reactant doublestherateofareaction, If rate =k[reactant] reactant. Therateequationis: be zeroorderwithrespecttothe reaction, thenthereactionissaidto reactant hasnoeffectontherateofa If tocompletion. further increases asthereactionmoves small,buttheerror isvery the error gone asmallwaytowardcompletion, occur. Providedthereactionhasonly a obtained astheinverseoftimefor Using aclocktechnique,therateis moment. particular estimate oftheratereactionatany obtain anincreasinglymoreaccurate timeperiods,wewould and shorter change inconcentrationovershorter second period.Bymeasuringthe the averagereactionrateduring10 Strictly speaking,thiswouldgiveus ever product concentration reaction, wecouldmeasurethe In ordertomonitortheprogressofa change inconcentrationofasubstance Rate ofreaction Clock technique Increasing concentration certain proportion ofthereactionto proportion certain doubling theconcentrationofa doubling theconcentrationofa doubling theconcentrationofa second orderwithrespecttothe y 10seconds. CHEMICAL REACTIONS at regular time intervals, say at regulartimeintervals, 136 of areactant time = 2 0 k = or a Variation ofreactionrate 2 1 are zero,first,andsecondorder The variationofreactionratewithconcentrationforreactionswhich % of reaction completed Clock technique for measuring reaction rates Increasing concentration 100 80 40 60 90 20 50 30 70 Reaction rate 10 0 1 2 2 3 2 3 1 1 3 Concentration of X second order first order zero order average reaction rate for 50%completion average reaction rate for 10% completion true initialrate Time/s 3 2 1 137

Rates of reaction: effect CHEMICAL REACTIONS of temperature 1 Key words effective collision The effect of temperature on different reactions enzyme kinetic energy polymer 1 Most reactions rate of reaction

Effect of temperature ● When a substance is heated, its particles gain kinetic energy and move around more quickly. The frequency of e t

a collisions increases, and because the r

n particles have a greater momentum, o i t

c the frequency of effective collisions a e

R also increases. The result is an increase in the rate of reaction. 1 Most reactions ● In most chemical reactions, the rate of Temperature reaction increases steadily with rising temperature. It is for this reason that chemical reactions are often heated. 2 Enzyme-catalyzed reactions 2 Enzyme-catalyzed reactions ● Enzymes catalyze chemical reactions with a high degree of specificity and efficiency. An enzyme molecule is a e

t polymer composed of a long chain of a r amino acids that folds over on itself, n o i

t giving it a particular shape. Reacting c a

e molecules, called the substrate, fit into R this shape rather like a key in a lock. ● Up to a point, the rate of an enzyme- catalyzed reaction increases with rising temperature in the same way as most other reactions. However, after Temperature reaching an optimum temperature at which the activity of the enzyme is 3 Explosive reactions greatest, the reaction rate rapidly falls. ● Heating an enzyme causes its shape to change, and thus the enzyme ceases to be able to catalyze the reaction. It is said to be denatured. 3 Explosive reactions e t ● a In an explosive reaction, the reaction r

n rate increases with rising temperature o i t

c up to some point where the reaction a e rate suddenly rises sharply. R mation Ltd. or Visual Inf

Temperature © Diagram © Diagram Visual Information Ltd. ● ● ● constant 2 ● ● ● reaction 1 activation energy Key words log kagainst reaction canbeobtainedbyplotting The gasconstant, Arrhenius equation. Arrhenius E E its unitisKtherefore The slopeofthegraphisnegative,and The constant, The Arrhenius E The constants calculation purposes. equation isthemostusefulfor ofthe the base10.Thelatterform oflogto andinterms logarithmic form The equationcanbeexpressedina the rateofreaction)totemperature. equation relatestherateconstant(not Ar by theSwedishchemistSvante The exactrelationshipwasproposed temperature. relationship betweenrateand suggest thatthereisanexponential in temperature.Thiswouldseemto a a As slope ( obtained bysubstitutingvaluesforthe Slope found fromtheslopeofgraph. The slopeofthegraphisequalto must beexpressedink Rate constantfor Plotting theArrhenius a a a reaction doubles for every 10Krise reaction doublesforevery slope kJmol K rhenius in1889.TheArrhenius / = = -1 CHEMICAL REACTIONS activation ener 2.303R general rule ofthumb,therate general rule 2.303 x0.008314 2.303 xR mol =- E E a -1 / therefore a 2.303R . / 1/T -1 2.303 R A 138 : and slope the temperature, R, =0.008314kJ ), log gy, E a elvin. E for agiven k A a , and , can alsobe can be T in the T , of temperature2 Rates ofreaction:effect 1 2 T R E A k –1 a Log (k/s ) Rate constantforreaction Plotting theArrheniusconstant = = = = = absolute temperature gas constant activation energy constant for thereaction (Arrhenius constant) rate constant for thereaction y In k=lnA–E k log k=log A–E = Ae –Ea/RT x slope = T –1 /k a /RT –1 x y a /2.303RT 139

Exothermic and CHEMICAL REACTIONS endothermic reactions Key words endothermic enthalpy 1 Exothermic exothermic product reactant

1 Exothermic ● In an exothermic reaction, energy is given out, and the temperature of the EA reaction mixture increases as the reaction proceeds. The products are at reactants a lower energy than the reactants. ● The energy released is due to a

y decrease in the enthalpy, ⌬H, of the g r

e system. Enthalpy is a measure of the n

E stored heat energy of a substance. Therefore, ⌬H is negative for an ∆H exothermic reaction. ● The following equation represents the combustion of methane in a good products supply of air: CH4(g) + 2O2(g) ➞ CO2(g) + 2H2O(g) ⌬H= -890 kJ mol-1 This is an exothermic reaction. 890 kJ of energy are released per mole of methane combusted. 2 Endothermic EA = activation energy ∆H = heat of reaction ● In an endothermic reaction, energy is 2 Endothermic taken in, and the temperature of the reaction mixture decreases as the reaction proceeds. The products are at a higher energy than the reactants. ● The energy taken in is due to an increase in the enthalpy, ⌬H, of the system. Therefore, ⌬H is positive for an endothermic reaction. ● The following equation represents the steam reforming of methane: EA CH4(g) + H2O(g) ➞ 3H2(g) + CO(g) ⌬H = +206 kJ mol-1

y This reaction is an endothermic g r

e reaction. 206 kJ of energy are taken in n

E per mole of methane reformed. products

∆H reactants mation Ltd. or Visual Inf © Diagram © Diagram Visual Information Ltd. ● ● ● ● change 2 ● ● 1 enthalpy dissociation Key words out whenthebondsareformed. in tobreakthebonds. bonds isbrok energy changewhenonemoleof 6,488 –8,542=2,054kJmol propane iscompletelycombusted The enthalpychangewhen1moleof 8,542 kJmol 6,488 kJmol reaction. estimate theenthalpychangeina how bondenthalpiescanbeusedto combustion ofpropanetoillustrate The tableatrightutilizesthecomplete bond. particular amount ofenergyneededtobreaka more usefultoknowtheaverage composed ofmorethanoneatom,itis F Bond enthalpy have adifferentbonddissociation are brokenanother, oneafter eachwill bondsinmethane example, iftheC-H environment ofthebond.For exact valuedependsonthelocal bond inamolecule.However, the CH(g) CH CH CH Average bondenthalpy or thisreason,inamolecule Estimating enthalpy ⌬ ⌬ ⌬ ⌬ 2 3 4 = H = H = H = H (g) (g) (g) CHEMICAL REACTIONS dissociation ➞ +335 kJmol +416 kJmol +470 kJmol +425 kJmol ➞ ➞ ➞ : C(g) +H(g) CH CH(g) +H(g) CH -1 -1 2 3 en. Itreferstoaspecific (g) +H(g) (g) +H(g) of totalenergyisgiven of totalenergyistaken 140 energy isthe -1 -1 -1 -1 -1 . Energy istakenintobreakbonds: C Complete combustion of propane. 2 1 6,488 –8,542=2,054 kJmol The enthalpy change when 1moleof propane iscompletely combusted is Energy isgivenoutwhenbondsareformed: dissociation energies Average bond 3 Total energy taken in O=O C–C C–H Bond Total energy taken in O–H C=O Bond H Average bondenthalpy Estimating theenthalpychangeinareaction. 8 (g) +5O odAverage bond Bond C–Cl C=C C–N C–O C–H C –C 2 (g) ➞ energy /kJmol dissociation Average bond 464 805 498 347 413 energy /kJmol dissociation Average bond 3CO 2 (g) +4H enthalpy /kJ –1 . mol 346 286 336 3 612 413 2 47 O(g) –1 –1 –1 8 6 of bonds Number 5 2 8 of bonds Number odAverage bond Bond C O=O O–H N–H H–H H–Cl =O in /kJmol Energy taken in /kJmol Energy taken 8,542 3,712 4,830 6,488 2,490 3,304 enthalpy /kJ 694 mol 498 464 391 436 432 8 05 –1 –1 –1 141

Catalysts: characteristics CHEMICAL REACTIONS

1 Characteristics of catalysts Key words activation energy Stoichiometry The overall stoichiometry of a reaction is unaltered. active site catalyst Specificity Catalysts may alter the rate of one reaction but have no effect on others. effective collision

Reaction mechanism A catalyst provides an alternative reaction pathway for a reaction to take place. Catalysts Chemical involvement A catalyst is chemically involved in a reaction. It is consumed ● during one step and regenerated in another. A catalyst does A catalyst is a substance that alters the not undergo a net chemical change, but it may change its rate of a chemical reaction but remains physical form. chemically unchanged by it. Equilibrium A catalyst speeds up the rates of both forward and backward reactions, and this speeds up the rate at which equilibrium 1 Characteristics of is attained. catalysts ● Yield A catalyst does not alter the yield of a reaction. Catalysts may be classified as homogenous or heterogeneous. Homogenous catalysts are in the same phase (solid, liquid, or gas) as the 2 Increasing reaction rate reactants; heterogeneous catalysts are in a different phase. ● A large number of reactions are catalyzed on the surface of solid catalysts. The surface provides active sites where reactions can occur. Thus, an increase in the surface area will increase the effect of the catalyst. Manganese Manganese dioxide 2 Increasing reaction rate dioxide remains at the end catalyst of the reaction ● Hydrogen peroxide decomposes very slowly on its own to form water and oxygen gas:

2H2O2(aq) ➞ 2H2O(l) + O2(g) 3 Distribution of the kinectic energies of reacting particles The rate of this reaction is greatly increased by adding manganese and the activation energies for catalyzed and uncatalyzed dioxide, MnO2. reactions ● Manganese dioxide acts as a catalyst and remains unchanged after all of the hydrogen peroxide has decomposed. E for catalyzed reaction ) A E ( 3 Activation energies y Extra fraction of particles with E >E

g A r ● A catalyst lowers the minimum energy,

e for catalyzed reaction n

e or activation energy (EA), required for

h E for uncatalyzed reaction t A i a reaction to occur. The frequency of w

s Fraction of particles with effective collisions is, therefore, e l

c for uncatalyzed increased, resulting in an increase in i E >EA t

r reaction

a the rate of a reaction. p f o r e b m u N mation Ltd. or

EA EA

Kinetic energy (E) Visual Inf © Diagram © Diagram Visual Information Ltd. ● ● ● 3 ● ● V 2 ● 1 Le Chatelier’s exothermic equilibrium catalyst Key words +5. reaction, itchangesbackfrom+4to from +5to+4.Intheoxidation oxidation stateofvanadiumchanges catalyst. Inthereductionreaction, T or transitionmetalcompounds. would otherwise bethecase. would otherwise achieved atalowertemperature than catalyst, areasonablerateofreactionis which equilibriumisattained.Usinga but itdoesincreasethespeedwith ammonia intheequilibriummixture, The catalystdoesnotaltertheyieldof ammonia inthe temperature wouldproducemore to This reactionis 74 and75): divided ironasthecatalyst(seepages manufacture ofammoniausesfinely The Haberprocessforthe and subsequent This reactioninvolvesthe pentoxide, the presenceofa dioxide isoxidizedtosulfurtrioxidein acid (seepages85and86).Sulfur step inthemanufactureofsulfuric The contactprocessisanimportant exist indifferent catalysts becauseortheirabilityto Catalysts equilibrium. but itwouldtak N Reaction catalyzed ransitional metalsareusefulas Iron ascatalyst principle 2 ⌬ Le Chatelier’s principle Chatelier’s Le + 2 = H CHEMICAL REACTIONS 0 3H 5 -92 kJmol 2 as catalyst are often are often V Fe(s) 2 O 142 5 e longertoreach . exothermic , equilibrium oxidation oxidation states catalyst. vanadium -1 2NH transition metals vanadium transition metals reduction oxidation state oxidation 3 a , reduction of the According low mixture, . metals Catalysts: transition 1 2SO (Energy profilesforthereactionN 3 2 Energy content (kJ) Transition metalsandreactioncatalyzed metal/compound –200 –300 –100 Iron ascatalystinHaberprocess Vanadium oxideascatalystincontactprocess 400 600 200 500 300 700 100 SO 2V Transition 0 V TiCl 2 Cu Fe Pt Ni 2 O 2 (g) +O 2 5 3 O + uncatalyzed reaction =668kJ activation energy for 4 + V 2 catalyzed reaction =212kJ activation energy for O O oxidation of ammoniainmanufacture of nitricacid oxidation of ethanol to ethanal Haber process onproduction of ammonia hydrogenation of alkenes inhardening of vegetable oils contact process inproduction of sulfuricacid polymerization of ethene to poly(ethene) 2 2 5 g 2SO (g) V 2 O 2 + 5 (s) 3H Reaction catalyzed 2 catalyzed reaction Fe(s) heat of reaction =–92kJ 2NH 2V SO 3 uncatalyzed reaction 2 3 ) O + 3 5 (g) V 2 O 4 N 2 2NH + 3H 3 2 143

Oxidation and reduction CHEMICAL REACTIONS

Key words 1 Oxygen oxidation oxidation state redox reaction Oxidation is the addition of oxygen to a substance reduction

Reduction is the removal of oxygen from a substance Evolving definition ● Over time, scientists have extended the definitions of oxidation and reduction. 1 Oxygen 2 Hydrogen ● Historically the terms oxidation and reduction were applied to reactions involving either the addition or the removal of oxygen. For example: ➞ Oxidation is the removal of hydrogen from a substance 2Cu(s) + O2 2CuO(s) copper is oxidized

Fe2O3(s) + 3CO(g) ➞ 2Fe(s) + 3CO2(g) Reduction is the addition of hydrogen to a substance iron is reduced 2 Hydrogen ● The terms were extended to include the removal or addition of hydrogen:

CH3-CH3(g) ➞ CH2=CH2(g) + H2(g) ethane is oxidized

3 Modern definition CH3COH(l) + H2(g) ➞ CH3CH2OH(l) ethanal is reduced 3 Modern definition Oxidation is the loss of electrons from a substance ● The terms oxidation and reduction are now used more widely to describe Reduction is the gain of electrons by a substance changes in oxidation state: Cu(s) ➞ Cu2+(aq) + 2e- copper is oxidized to copper(II) Fe3+(aq) + e- ➞ Fe2+(aq) iron(III) is reduced to iron(II) ● This definition covers all of those reactions involving the gain or loss of 4 Redox reaction oxygen and other reactions that do not involve oxygen. oxidation 4 Redox reaction ● Reactions that involve a reduction must also involve an oxidation. If one reactant is reduced, then another must 2+ 2+ be oxidized. Such reactions are Mg(s) + Cu ➞ Mg (aq) + Cu(s) described as redox reactions. mation Ltd. or Visual Inf reduction © Diagram © Diagram Visual Information Ltd. ● ● ● ● reactions 3 ● ● 2 ● ● ● ● 1 ● Redox reactions reduction redox reaction oxidation displacement Key words The resultisabalancedequation (d). 2 entire reactionhastobemultipliedby In ordertobalancetheequation, losing 1electron. gaining twoelectronsandiron(b)is In theexampleatright,bromine(a)is gained. electrons lostmustequalthe In balancingredoxreactions,the atoms bygainingtwoelectrons. Copper ionsarereducedtocopper losing twoelectrons. Zinc atomsareoxidizedtozincionsby Zn(s) +Cu reaction reaction iscalleda solution ofitssalts.Thistype ions ofalessreactivemetalfrom A tometaloxides. converted ofallmetalswhentheyare This istrue ions bygainingtwoelectrons. Oxygen atomsarereducedtooxide electrons. magnesium ionsbylosingtwo Magnesium atomsareoxidizedto 2Mg(s) +O magnesiumoxide: forms When magnesiumisheatedinair, it collectively refer always occurtogetherandare Reduction reactions. Oxidation andreduction Balancing redox Electron transfer reaction (c). more reactivemetaldisplacesthe CHEMICAL REACTIONS : 2+ and 2 (g) (aq) 144 oxidation ➞ red toas ➞ 2MgO(s) displacement Zn 2+ (aq) +Cu(s) redox reactions Redox reactions1 2Mg +O 2Fe Br 2Fe Fe (a) Theoxidizing agent isBr Br 3 Redox equations for thereaction Cu Zn(s) When powered zincisaddedto copper sulfate (II)solution, anexothermic reaction occurs Zn(s) +Cu 2 O 2Mg up by themetal 4Na +O The metal isoxidized andthemetal isreduced. The oxygen takes theelectrons given 1 When metals react withoxygen they form oxides (d) Balance equation (c) Redox reaction (b) The reducing agent isFe Redox reactions: oxidation andreduction Balancing redox reactions Electron transfer inredox reactions 2 2+ 2 2 2+ + 2+ 2+ + +

(aq) 4e

+Br 2e 2e – +2e 2 – – 2 2+ 2 (aq) – 2+ 2

→ → → → → → → → → → → → Zn 2Fe Zn 2Mg 2Br Cu(s) 2O 2(Na 2Mg 2Fe 2Br Fe 3+ 2+ 2+ 2– – – 3+ 3+ +e 2+ 2+ (aq) (aq) 2 +2Br +2e ) +4e +2O 2 O +2e +Cu(s) – 2– – – 2– – – 145

Redox reactions 2 CHEMICAL REACTIONS

Key words 1 The reaction of metals with non-metals redox reaction Fe + S → Fe2+S2–

Iron and sulfur

Fe → Fe2+ + 2e– 1 Metals with non-metals ● Iron undergoes redox reactions with S + 2e– → S2– non-metals. Iron and sulfur: Redox equation Fe(s) + S(s) ➞ Fe2+S2-(s) Iron atoms are oxidized to iron(II) ions by losing two electrons. 2Fe + 3Cl2 → 2FeCl3 Sulfur is reduced to sulfide ions by gaining two electrons. Iron and chlorine Iron and chlorine: 3+ - 2Fe(s) + 3Cl2(s) ➞ 2Fe Cl 3(s) 2Fe → 2Fe3+ + 6e– Iron atoms are oxidized to iron(III) ions by losing three electrons. 3Cl + 6e– → 6Cl– Chlorine is reduced to chloride ions by 2 gaining one electron. Redox equation 2 Metals with water ● Metals are oxidized when they react with water. 2 The reaction of metals with water Metal + water ➞ metal hydroxide + hydrogen ➞ Ca + 2H O → Ca2+(OH–) + H Ca(s) + 2H2O(l) 2 2 2 Ca(OH)2(aq) + H2(g) + - H2O(l) H (aq) + OH (aq) + 2+ Calcium and water Ca(s) + 2H (aq) ➞ Ca (aq) + H2(g) In the example at left, calcium atoms Ca → Ca2+ + 2e– are oxidized to calcium ions by the loss of two electrons. Hydrogen ions – – are reduced to hydrogen atoms by 2H2O + 2e → 2OH + H2 gaining one electron.

Redox equation 3 Metals with acids ● Metals are oxidized when they react with acids. 3 The reaction of metals with acids Metal + acid ➞ metal salt + hydrogen Zn(s) + 2HCl(aq) ➞ ZnCl2(aq) + H2(g) + 2+ Zn(s) + 2H (aq) ➞ Zn (aq) + H2(g) Zn(s) + 2H+ → Zn2+ + H In the example at left, zinc atoms are (aq) (aq) 2 → oxidized to zinc ions by the loss of two electrons. Hydrogen ions are reduced The reaction of zinc to hydrogen atoms by gaining one Zn → Zn2+ + 2e– electron. mation Ltd. or 2H+ + 2e– → H2 Visual Inf

Redox equation © Diagram © Diagram Visual Information Ltd. ● ● 2 ● ● ● ● ● ● reactions 1 redox reaction reactivity series Key words reduced. lower inthereactivityserieswill be while theionsofmetalthat is the reactivityserieswillbeoxidized, reactivities. Themetalthatishigherin exter cell, thedirectionofelectronsin When anytwometalsareplacedina ions arereducedtocopperatoms. oxidized tozincions,whilecopper reactivity series Zinc ishigherthancopperinthe charged andnegativelyions. solutions asaflowofpositively passesthroughionic Electric current zinc sulfatesolution. from thecoppersulfatesolutionto negative ionsintheoppositedirection solution tothecoppersulfate,and positive ionsfromthezincsulfate Ions flowthroughthesaltbridge: negatively chargedelectrons. circuitasaflowof wire intheexternal passesthroughthe Electric current metal onthecopperrod. solution andaredepositedascopper atoms. Thecopperionscomeoutof two electronstobecomecopper At thecopperrod,ionsgain The zincionspassintosolution. through thebulbtocopperrod. electrons passalongthewireand electrons tobecomezincions.The At thezincrod,atomslosetwo salt bridge. their salts,connectedbyawireand metals rods,suspendedinsolutionsof using asimplecellconsistingoftwo redox reactions The movementofelectronsduring Electron transferinredox Reaction equations CHEMICAL REACTIONS nal circuitdependsontheir 146 . can bedemonstrated Zinc atomsare reactions Demonstrating redox e d c b around thecircuit Movement of charge Experimental set-up Copper ionsare reduced to a deposit of red-brown 2 a 1 b a c copper rod nitrate asasalt bridge filter paper soaked inpotassium electron flow zinc sulfate solution zinc rod Electron transfer inredox reactions Reaction equations Cu Zn(s)Cu + 2e Zn – 2+ 2+ NO (aq) – 3 Zn(s) + 2e h 2+ – → → → i h g f movement of positive charge (cations) and anions) movement of negative charge (electrons small lightbulb copper sulfate solution Cu(s) Zn Zn i 2+ 2+ (aq) (aq) SO 4 2– +Cu(s) +2e K + CU 2e 2+ – – d g e f 147

Assigning oxidation state CHEMICAL REACTIONS

1 Oxidation state Key words

Component Oxidation state oxidation state transition metals uncombined elements 0

Group 2 metals in compounds +2

Group 1 metals in compounds +1 combined hydrogen except in metal hydrides +1 1 Oxidation state combined hydrogen in metal hydrides –1 ● The ability of transition metals to combined halogens –1 exhibit different oxidation states in different compounds is central to the combined oxygen –2 behavior of these elements. ● The oxidation state of simple ions is given by the charge they carry, e.g.: Na+ has an oxidation state of +1 O2- has an oxidation state of -2 22 Tetrachlorocuprate ion ● The situation is more complicated in a complex ion. The oxidation state of the central atom in a complex ion is 2– the charge that the ion would have if it CuCl were a simple ion. This is found by 4 adding the oxidation states of the various components in the complex ion. the tetrachlorocuprate ion contains the transition metal copper 2 Tetrachlorocuprate ion ● Total oxidation number due to chlorine = 4 x -1 = -4. ● Overall charge on the ion = -2. ● Oxidation state of the central copper 33 Manganate ion atom = -2 – (-4) = +2. ● This complex ion is more correctly – called the tetrachlorocuprate(II) ion. MnO 3 Manganate ion 4 ● Total oxidation number due to oxygen = 4 x -2 = -8. ● Overall charge on the ion = -1. the manganate ion contains the transition metal manganese ● Oxidation state of the central manganese atom = -1 – (-8) = +7. ● This complex ion is more correctly called the manganate(VII) ion. 4 Dichromate ion ● Total oxidation number due to oxygen 44 Dichromate ion = 7 x -2 = -14. ● Overall charge on the ion = -2. ● Total oxidation state of the two central 2– chromium atoms = -2 – (-14) = +12. Cr O ● Oxidation state of each chromium

2 7 mation Ltd.

atom = +12 / 2 = +6. or ● This complex ion is more correctly

CHEMISTRY OF CARBON The allotropes of carbon: Key words diamond and graphite allotrope carbon diamond Diamond fullerenes graphite Bond angle 109.5° Bond length 0.154 nm

Carbon allotropes ● Carbon exists in three allotropes: diamond, graphite, and fullerenes. 1 Diamond ● In diamond, each carbon atom is covalently bonded to four other carbon atoms. ● The four bonds are directed toward the corners of a pyramid or tetrahedron, and all bonds are the same length, 0.154 nm. The angle between any two bonds is 109.5°. ● All four of the outer electrons on the carbon atom form bonds with other carbon atoms so there are no mobile electrons. Diamond does not, therefore, conduct electricity. ● Diamond has a rigid structure and is very hard. 2 Graphite ● The carbon atoms in graphite are arranged in layers consisting of interlocking hexagons in which each Graphite carbon atom is covalently bonded to Bond angle 120° three other carbon atoms. The length Bond lengths of the bond is 0.141 nm, and the angle – in layers 0.141 nm – between layers between bonds is 120°. 0.335 nm ● The fourth outer electron on each carbon atom forms bonds with adjacent layers. The bond length is much greater than between carbon atoms within a layer. ● The electrons between the layers are mobile; therefore, graphite conducts electricity. Also, the layers are able to slide over each other relatively easily. ● Graphite is soft. mation Ltd. or Visual Inf © Diagram 149

The allotropes of carbon: CHEMISTRY OF CARBON fullerenes Key words allotrope fullerenes buckyball graphite Buckyball carbon nanotube

Fullerenes ● Fullerenes are allotropes of carbon in the form of a hollow sphere or tube. Spherical fullerenes are sometimes called buckyballs, and cylindrical fullerenes are called nanotubes. ● Because the allotrope was only discovered in the late twentieth century, its physical and chemical properties are still being studied. ● Fullerenes are not very reactive and are only slightly soluble in many solvents. They are the only known allotrope of carbon that can be dissolved. Buckminsterfullerene ● This form of carbon is composed of 60 carbon atoms bonded together in a polyhedral structure composed of pentagons and hexagons. The molecules are made when an electric arc is struck between graphite electrodes in an inert atmosphere. This method also produces small amounts of other fullerenes that have less symmetrical molecular structures,

such as C70. ● Buckminsterfullerene was first identified in 1985 and named after the architect Richard Buckminster Fuller Nanotube because of the resemblance of its structure to the geodesic dome. ● The substance is a yellow crystalline solid that is soluble in benzene, an organic solvent. ● It is possible to trap metal ions within

the C60 sphere. Some of these structures are semiconductors. Nanotubes ● Nanotubes, first identified in 1991, are long thin cylinders of carbon closed at either end with caps containing pentagonal rings. mation Ltd.

● Nanotubes have a very broad range of or electronic, thermal, and structural

properties that change depending on Visual Inf the kind of nanotube (defined by its diameter, length, and twist). © Diagram

150

CHEMISTRY OF CARBON The carbon cycle

Key words a atmosphere photosynthesis b carbon respiration carbon cycle chlorophyll glucose

The carbon cycle ● Carbon is the fourth most abundant element in the Universe.

● The total amount of carbon on planet

Earth is fixed. The same carbon atoms Respiration Photosynthesis

have been used in countless other carbon sunlight glucose+oxygen→ carbon +water+energy +water glucose+oxygen molecules since Earth began. The dioxide dioxide chlorophyll carbon cycle is the complex set of processes through which all carbon C H O + 60 → 6CO + 6H O 6CO + 6H 0 → C H O + 6O atoms rotate. 6 12 8(aq) 2(g) 2(g) 2 (I) 2(g) 2 (I) 6 12 6(aq) 2(g) ● Carbon exists in Earth’s atmosphere primarily as carbon dioxide. ● All green plants contain chlorophyll, a pigment that gives them their characteristic color. During photosynthesis, chlorophyll traps energy from sunlight and uses it to convert carbon dioxide and water into glucose and oxygen. ● Carbon is transferred from green plants to animals when animals eat plants or other animals. c ● All animals and plants need energy to drive their various metabolic d processes. This energy is provided by respiration. During this process, glucose reacts with oxygen to form e carbon dioxide and water. These waste products are subsequently released into the atmosphere. In essence, respiration is the opposite process to photosynthesis. ● When plants and animals die, their g

bodies decompose. In the presence of a a a air, the carbon they contain becomes a carbon dioxide, which is released into a aa the atmosphere. a a a ● When plants and animals decay in the a aa absence of air, carbon cannot be a a a a a aaa converted into carbon dioxide. a Instead, it remains and forms fossil a a a a aaa a aaa aa a a a a fuels such as coal, crude oil, and f natural gas. mation Ltd. ● or When fossil fuels are burned, the a carbon dioxide in the air carbon they contain becomes carbon b sunlight c plants take in carbon dioxide and give out oxygen

Visual Inf dioxide and is released into the d animals take in oxygen, eat plants and vegetables, and breath out CO2 atmosphere. e death and decay f carbon compounds (e.g., in oil and coal)

Laboratory preparation CHEMISTRY OF CARBON of carbon oxides Key words carbonate carbon dioxide 1 Preparation of carbon dioxide carbon monoxide c

Carbon oxides ● The most common forms of carbon oxides are carbon dioxide, which is instrumental in the carbon cycle, and d carbon monoxide, a colorless, odorless gas that is the result of the incomplete combustion of fuels. They a b can be prepared in the laboratory using the following techniques. 1 Carbon dioxide 2 Preparation of dry carbon dioxide ● Carbon dioxide is formed when a metal carbonate reacts with a dilute e acid: metal carbonate + dilute acid ➞ metal salt + carbon dioxide + water ● When calcium carbonate (marble chips) reacts with dilute hydrochloric acid:

CaCO3(s) + 2HCl(aq) ➞ CaCl2(aq) + CO2(g) + H2O(l) f e ● Carbon dioxide is not very soluble in water, so it can be conveniently collected over water. 3 Preparation of carbon monoxide 2 Dry carbon dioxide ● Carbon dioxide can be dried by passing it through concentrated sulfuric acid and collected by downward delivery (upward displacement) because it is denser than air. j g 3 Carbon monoxide ● Carbon monoxide is formed by the dehydration of ethanedioic (oxalic) acid using concentrated sulfuric acid: i conc. sulfuric acid HOOC-COOH(l) ——————————➞ h CO2(g) + CO(g) + H2O(l) ● Acid residues and carbon dioxide are removed by passing the gas through a potassium hydroxide solution. Carbon mation Ltd.

monoxide can be collected over water or because it is only slightly soluble. a marble chips f concentrated sulfuric acid b dilute hydrochloric acid g ethanedioic (oxalic) acid crystals and concentrated sulfuric acid Visual Inf c carbon dioxide h heat d water i concentrated potassium hydroxide solution

CHEMISTRY OF CARBON The fractional distillation Key words of crude oil fractional distillation hydrocarbon 1 Fractional distillation of crude oil d

Fractional distillation e ● Fractional distillation is one of c several processes used to refine crude f oil. Refining converts crude oil into a range of useful products. ● Crude oil is a complex mixture of hydrocarbons. During fractional g distillation, this mixture is separated into a series of fractions (components) on the basis of boiling point. ● The crude oil is passed through a furnace, where it is heated to 400°C and turns mostly into vapor. The gases pass into a distillation column within which there is a gradation of temperature. The column is hottest at b the bottom and coolest at the top. h ● Hydrocarbons with the highest boiling a points are the first to condense at the bottom of the column, along with any remaining liquid residue from the crude oil. This fraction provides 2 Crude oil composition (percent yields and uses of oil) bitumen for use in road building. ● Rising up the column, other fractions condense out: first diesel oil, then kerosene, and finally gasoline. All of i 18% i 21% i 21% these fractions are used as fuels. ● The hydrocarbons with the lowest j 11.5% j 13% 15% boiling points remain as gases and rise j to the top of the column. This fraction is used as a fuel in the refinery. k 18% k 20% 21% ● The hydrocarbon vapor moves up the k column through a series of bubble caps. At each level, the hydrocarbon vapor passes through condensed hydrocarbon liquid. This helps to l 52.5% l ensure a good separation into the 46% l 43% various fractions. Crude oil composition ● Crude oil varies in composition, Arabian Iranian Arabian depending on where it was obtained. heavy heavy light mation Ltd.

or Fractional distillation of different crude oils provides different proportions of a crude oil g diesel oil (260°C) the various fractions. b heater h residue — bitumen tar (400°C) Visual Inf c bubble cap i gasoline and chemical feedstock d refinery gas j kerosine e gasoline (110°C) k gas oil f kerosine (180°C) l fuel oil © Diagram 153

Other refining processes CHEMISTRY OF CARBON

Key words 1 Other refining processes alkane isomerization fractional distillation alkene polymerization catalytic cracking reforming fractional residfining distillation

1 Other processes ● Other refining processes are used to modify the products of fractional isomerization reforming catalytic polymerization residfining distillation. These include cracking isomerization, reforming, catalytic cracking, polymerization, and residfining. 2 Isomerization 2 Isomerization CH3—CH2—CH2—CH2—CH2—CH3 CH3—CH2—CH2—CH—CH3 ● Isomerization changes the shape of hydrocarbon molecules. For example, CH3 pentane 2-methylbutane pentane is converted into 2- methlybutane.

3 Reforming 3 Reforming Dehydration ● Reforming converts straight chain molecules into branched molecules in CH3 CH3 order to improve the efficiency of CH C gasoline. One type of reaction involves the dehydration of saturated CH2 CH2 CH CH compounds to unsaturated + 3H2 compounds. Another involves the CH CH CH CH 2 2 cyclization of hydrocarbons. CH CH 2 4 Catalytic cracking methylcyclohexane methylbenzene ● In general, smaller hydrocarbon Cyclization molecules, such as those in gasoline, CH3 are in greater demand than larger CH ones. Catalytic cracking redresses this balance by breaking (cracking) large CH —CH —CH —CH —CH —CH —CH CH CH 3 2 2 2 2 2 3 2 2 alkane molecules into smaller alkane and alkene molecules. heptane CH2 CH2 5 Polymerization CH2 methylcyclohexane ● Polymerization combines small molecules to form larger molecules that can be used to make various 4 Catalytic cracking products. Octane ➞ propane and pent-1-ene Residfining CH CH CH CH CH CH CH CH ➞ CH CH CH + CH CH CH CH=CH 3 2 2 2 2 2 2 3 3 2 3 3 2 2 2 ● Resifining is the process used on the octane propane pent-1-ene residue fraction to convert it into usable products. It also removes mation Ltd.

5 Polymerization impurities that would damage the or catalyst used in catalytic cracking.

Two propene molecules combine to form hexene Visual Inf

CHEMISTRY OF CARBON Carbon chains

Key words 1 Catenation alkane catenation alkene van der Waals Chain length alkyne forces 23 8 bond HH HHH HHHHHHHH carbon HCCH HCCCH HCCCCCCCCH 1 Catenation HH HHH HHHHHHHH ● Carbon has the ability to form long chains of carbon atoms in its compounds. This is called catenation. 2 Melting and boiling points of some chains 2 Melting and boiling points Chain length 3616 ● Forces of attraction, called van der HHH HHHHHH Waals forces, exist between molecules. As molecular size increases, there is HCCCH HCCCCCCH C16H34 more overlap between the molecules, and the intermolecular forces of HHH HHHHHH attraction increase. C3H8 C6H14 ● In order to melt and to boil, the forces of attraction between molecules must be overcome. The greater these m.p./°C –187 –94 18 forces, the more energy is needed. This is reflected in a steady increase in b.p./°C –41 69 287 melting point and boiling point as molecules increase in size. 3 Types of bonds 3 Types of bonds ● A carbon atom may form one, two, or HH three bonds with another carbon atom in its compounds. These bonds are HCCH CC C–C described as single bonds ( ), HH double bonds (C=C), and triple bonds Alkanes (CϵC). Single bond ● Alkanes contain only carbon–carbon single bonds. ● Alkenes contain a carbon–carbon double bond. H H ● Alkynes contain a carbon–carbon triple CC CC bond. H H ● Alkanes, alkenes, and alkynes are all hydrocarbons since they consist only Alkenes of hydrogen and carbon atoms. Double bond mation Ltd. or HCCH CC Visual Inf

Naming hydrocarbons CHEMISTRY OF CARBON

1 Chain length gives first part of name Key words alkane alkene Chain length C1 C2 C3 C4 C5 C6 alkyne functional group First part of name meth- eth- prop- but- pent- hex- hydrocarbon

Naming hydrocarbons ● The name of a hydrocarbon indicates 2 Functional group gives second part of name the number of carbon atoms in the molecule and what sort of carbon–carbon bonds is present. Alkane Alkene Alkyne H 1 Chain length Functional group CC CC ● CH The first part of name is determined by the number of carbon atoms in the H molecule. The same prefixes are used for all groups of organic compounds. Second part of name -ane -ene -yne 2 Functional group ● The second part of the name is determined by the type of carbon–carbon bonds present. Each 3 Examples of organic compound names functional group has a unique suffix. ● The position of the functional group in a carbon chain is identified by Molecule Chain length Functional group Name numbering the carbon atoms in the carbon chain. H H 3 Examples of compound HCH 1 meth- CH -ane methane names ● The first two examples in the diagram H H are alkanes. If there is one carbon atom in the molecule it is: “meth” (1 carbon atom in the chain) HHHH H + “ane” (for alkane): methane. If there are four carbon atoms in the 4 but- CH -ane butane HCCCCH molecule it is: HHHH H “but” (4 carbon atoms in the chain) + “ane” (for alkane): butane. ● The third example is propane, an H alkene with three carbon atoms: “pro” (3 carbon atoms in the chain) H CH + “ene” (for alkene). 3 prop- CC -ene propene ● The fourth example is ethyne, an HCC alkyne with a two carbon chain: HH “eth” (2 carbon atoms in the chain) + “yne” (for alkyne). mation Ltd.

CHEMISTRY OF CARBON Table of the first six Key words alkanes alkane van der Waals homologous forces series Alkane Methane Ethane Propane hydrocarbon

Formula CH C H C H The first six alkanes 4 2 6 3 8 ● The alkanes f orm an homologous series of compounds that have the general formula CnH2n+2, where n is a H HH HHH positive integer. Each alkane molecule Structural HCH HCCH HCCCH differs from the previous one in the formula H HH HHH series by -CH2-. ● They have similar chemical properties and show a gradation of physical properties, such as melting point and Boiling –164 –87 –42 boiling point, as the molecular size point (°C) increases. ● Alkane molecules are attracted to each other by van der Waals forces. As molecular size increases, there is more Physical state at room Gas Gas Gas overlap between the molecules, and temperature the intermolecular forces of attraction increase. ● Alkane molecules are frequently shown as having a flat two-dimensional Molecular structure because this is easy to draw, model but in reality, the four bonds around each carbon atom are directed toward the corners of a tetrahedron. The Alkane Butane Pentane Hexane angle between any two bonds is 109.5°. ● Alkanes are relatively unreactive Formula C4H10 C5H12 C6H14 substances when compared with other groups of hydrocarbons. Their most important reaction is combustion, and they are the main constituent of a HHHH HHHHH HHHHHH range of fuels. Natural gas is largely Structural HCCCCH HCCCCCH HCCCCCCH formula composed of methane: HHHH HHHHH HHHHHH CH4 + 2O2 ➞ CO2 + 2H2O ● In a good supply of air, hydrocarbons burn to give carbon dioxide and water. In a restricted supply of air, carbon Boiling point (°C) 03669 monoxide and/or carbon may be formed:

C2H6 + 2O2 ➞ CO + C + 3H2O

Physical state at room Gas Liquid Liquid temperature mation Ltd. or

Table of the first five CHEMISTRY OF CARBON alkenes Key words addition reaction van der Waals alkene forces functional group homologous series

r The first five alkenes a l l e u ● d c The alkenes form an homologous o e l m o series of compounds with the general M formula CnH2n, where n is a positive integer. Each alkene molecule differs from the previous one in the series by

-CH2-. ● Alkene molecules are attracted to each other by van der Waals forces. As molecular size increases, there is more e m

r overlap between the molecules, and o l u d d o a t i i r c s s s a

i the intermolecular forces of attraction r t u u s a a a e a y q q p increase. The series thus shows a h i i G G G e t P m L L a e

t gradation of physical properties, such t s as melting point and boiling point. ● Alkenes all contain the same

) functional group, a carbon–carbon C g ° 4 C=C n 7 ( double bond, represented by . i 4 6 l 0 0 t i 4 n 1 – o ● 6 3

i The bonds around each of the carbon – B – o

p atoms in a carbon–carbon double bond are in the same plane and directed toward the corners of an equilateral triangle. The angle between H H H H H H H H H H any two bonds is 120°. C C C C C ● Alkenes undergo combustion in the C H same way as alkanes. However, they C C H C C H H l

a have other chemistry resulting from a r H H l C H H C C H H C H H H H u u t the reactive carbon–carbon double c m r u C H H r H C C H H H H

o bond. t f S ● Alkenes undergo addition reactions in H H C H H H C which a molecule is added across the C H H

H carbon–carbon double bond. For example, ethene undergoes the H following addition reactions:

CH2=CH2 + H-H ➞ CH3-CH3 s

e ethene + hydrogen ➞ ethane l f m u o o c t r e a e l 3 5 2 b 6 4 o n CH2=CH2 + H-OH ➞ CH3-CH2-OH o m m b u r ethene + steam ➞ ethanol r e N a p c

CH2=CH2 + H-Br ➞ CH3-CH2Br a 2

0 ethene + hydrogen bromide ➞ l 8 4 6 1 1 u H H H

H bromoethane H m 2 3 4 r 6 5 mation Ltd. o C C C F or C C

CH2=CH2 + Br-Br ➞ CH2Br-CH2Br ethene + bromine ➞ 1,2-dibromoethane e e Visual Inf e e e n e n n n e n n e e e t e p e k t x n l o h e u r e t A B P H E P © Diagram 158

CHEMISTRY OF CARBON Ethene

Key words 1 Dehydration of ethanol to produce ethene alkene geometric ethane isomerism a concentrated sulfuric acid a b ethanol ethene halogens c heat ethanol isomer d alkali — to remove impurities e water f ethene Ethene ● Ethene is the first member of the alkene series. It is a colorless, flammable gas. f

1 Preparation b ● In the laboratory, ethene can be made by the dehydration of ethanol using concentrated sulfuric acid. e 2 Structure ● Ethene, like all alkenes, contains a c d carbon–carbon double bond about which rotation is impossible. 3 Isomerism -H2O CH3CH2OH ➞ CH2=CH2 ● Isomers are compounds having the ethanol ethene same molecular formula and relative molecular mass but different three- dimensional structures. ● The existence of two compounds with 2 Structure 3 Isomerism the same molecular formula but where H H H Br groups are distributed differently H H around a carbon–carbon double bond CC CC CC is described as geometric isomerism HH Br H Br Br or cis / trans isomerism. Ethene Trans-1, 2-dibromoethene Cis-1, 2-dibromoethene ● The prefix “cis” is used when the substituent groups (an atom or group of atoms substituted in place of a hydrogen atom or chain) of a 4 Reactivity hydrocarbon are or the same side of a plane through the carbon–carbon double bond. The prefix “trans” is CH2 = CH2 + Cl2 CH2Cl—CH2Cl used when the substituent groups are on the opposite side. Reaction with chlorine to form 1, 2-dichloroethane ● In trans-1,2-dibromoethene the bromine atoms are on opposite sides of a plane through the carbon–carbon Ni double bond. ● In cis-1,2-dibromoethene the bromine CH2 = CH2 + H2 CH3CH3 atoms are on the same side. Reaction with hydrogen to form ethane 4 Reactivity ● The carbon–carbon double bond in mation Ltd.

or ethene is very reactive and will undergo various addition reactions. CH = CH + HX CH3CH2X Visual Inf Ethene reacts with: halogens (such as 2 2 chlorine) to form 1,2-dihaloethane, hydrogen to form ethane, and Reaction with hydrogen halides to form haloethane

Polymers CHEMISTRY OF CARBON

Key words 1 Types of branching addition polyethene polymerization polymer A bakelite polymerization ethene B Polymers ● A polymer is a large organic molecule composed of repeating carbon chains. The physical properties of a polymer Polymer with few branched chains, depend on the nature of these carbon e.g., high-density polyethene chains and how they are arranged. 1 Types of branching ● A certain amount of side branching occurs during polymerization, C depending on the reaction conditions. ● Low pressure and low temperature results in a high-density polymer. Polymer with many branched chains, ● Very high pressure and moderate e.g., low-density polyethene temperatures produce a low-density polymer. ● In high-density polymers, the carbon chains are unbranched, and they can be packed closely together forming a Polymer with much cross-linking, dense substance, e.g., high-density e.g., bakelite polyethene (1A). ● In low-density polymers, the carbon chains are branched, and it is not possible to pack them as closely 2 Additional polymerization (illustrating how ethene can be together, e.g., low-density polyethene restructured to form poly(ethylene) i.e., polyethene) (1B). ● In polymers like bakelite, there are cross links between the carbon chains, H H H H H H producing a hard, rigid structure (1C). CC CC CC 2 Addition polymerization H H H H H H ● Ethene forms a polymer by a process called addition polymerization. ● In this process, one of the bonds from the carbon–carbon double bond is HH HH HH used to form a bond with an adjacent molecule. This process is repeated CC CC CC many times, resulting in long chains containing thousands of carbon atoms. HH HH HH

CHEMISTRY OF CARBON Polymers: formation

Key words 1 Restructuring of propene to make poly(propene) alkene polymer monomer CH3 H CH3 H CH3 H CC CC CC Monomers ● Monomers are the basic units from H H H H H H which a polymer is made. ● The systematic name for a polymer is CH3 HHHCH3 CH3 derived from the name of the monomer. For example, polypropene CCCCCC is “poly” (for polymer) + the alkene propene. HHHHHH ● The diagrams at right illustrate the formation of some alkene polymers. 2 Restructuring of chloroethene to make poly(chloroethene) 1 Forming polypropene i.e., polyvinylchloride ● Propene molecules combine to form Cl H Cl H Cl H polypropene. ● Most polypropene is produced as a CC CC CC monopolymer (a polymer formed from propene only). H H H H H H

2 Forming Cl HCl H Cl H polychloroethene ● Chloroethene molecules combine to CCCCCC form polychloroethene. ● 1,2-dichloroethane is made by HHHHHH chlorinating ethene. This product is then cracked to form chloroethene. 3 Poly(phenylethene) 3 Forming C H H C H H C H H polyphenylethene 6 5 6 5 6 5 ● Phenylethene molecules combine to CC CC CC form polyphenylethene. H H H H H H ● Phenylethane is made from ethene and benzene by a Friedel-Crafts reaction using aluminum(III) C6H5 H C6H5 H C6H5 H chloride/hydrochloric acid catalyst. This is dehydrogenated to give the CCCCCC phenylethene monomer. HHHHHH 4 Forming polytetrafluoroethene ● Tetrafluoroethene molecules combine 4 Poly(tetrafluoroethene) to form polytetrafluoroethene. F F F F F F ● Trichloromethane is produced by the reaction of methane with controlled CC CC CC amounts of chlorine/hydrochloric acid. F F F F F F This is reacted with anhydrous hydrogen fluoride in the presence of mation Ltd. or antimony(III) chloride to give F FFFFF chlorodifluoromethane, which is CCCCCC Visual Inf subsequently cracked to produce tetrafluoroethene. F FFFFF © Diagram 161

Polymers: table of CHEMISTRY OF CARBON properties and structure Key words monomer polymer polymerization 5 r e O 3 H N 6 m l 3 H o H C C H H H 3 H H F F H C C n H H C o C m C C C C C C O C

f Polymers o e

C ● C C r C C C C Most polymers have common names u t H H c that are used in everyday language. F F H H H H H H H H H H u r

t ● The uses of polymers depend on their S properties. Classification ● There are several ways in which n o i h t polymers can be classified. t n s a i s l o n e i

w ● u l t

a Heat. Thermoplastics soften when i s , t a p d l n s s x i e u e e n e heated and harden on cooling, so they s l l d s t s o d e c c n n l s i i n s i n a t t g i

a can be reshaped many times without b a e l r r r p n a s i e g a a o x s ; s c t t f U r e c changing their chemical structure. s r a u d d i d i i e , g t o d r o i f s n g g b a e t c b i i i Thermosets are chemically altered on y a s s f b r r e a k o f t u b s t c d d g g u u i

e heating and produce a permanently g t d n n n n t c i r s i i i n i t s n a a i t l d d - s t a l l w s hard material that cannot be softened o n b a o o m m a r o l l l o n i o u i i w s n a p o c f m m f by heating. ● Method of polymerization. Addition polymers are usually formed from t a

e monomers containing a –CH=CH- unit h o

t to which different atoms or groups are e l attached. On polymerization, one of s b e a i t t the carbon–carbon bonds becomes a s r p e d a

p bond to another unit. Condensation n e o a h s r ; y y r t c t t y P polymers are formed from n i i e n t t i o s s e b i u s i r n n t

f condensation reactions in which a b n a e e c e i l e g p d d e r l b f d s n small molecule, sometimes but not i t h h n t o x i g g r w w a e r i i t r l o o always water, is lost. s t l b f h h l ● Formula. Homopolymers are formed from one monomer unit. Co-polymers are formed from two or more e

m monomers. a ) ) n e

e ● d

n Chemical structure. Linear chains may n i o r e o h m l have straight, zigzag, coiled, or t h e m c o l o random spatial arrangements. r e y c o n n r i u

e Branched chains have side branch l e e v l e f n y y n a l m e r p e chains attached to the main chains. r o y t x l o h y e n p e r t t o t ( a p e p s Cross-linked chains have two or three l y E P i l s y y y C F r l l l r o c T V e o o o dimensional cross-linkage between p A P ( P P P P P chains.

e ● Steric structure. Isotactic: in which all m - l a y

n side groups are on the same side of ) h ) e ) t l e c e i i e n t

r the main chain. Syndiotactic: in which n t e a m mation Ltd. i e - h n ) h or t m each alternative side group has the 2 t e e - e ) ) e l e ) l t n n e e y e o y s e a same orientation. Atactic: in which n n t r h n y p p e e a t o s e l o o e o h h Visual Inf r h r there is no specific pattern to the t t r h n p p p m e c e e e ( ( ( ( ( ( ( p y y y y y y y

CHEMISTRY OF CARBON Functional groups and Key words homologous series alcohol homologous alkene series carboxylic acid oxidation Functional group Example ester functional group 1 Alkenes Propene

Functional groups H H ● A functional group is the atom or group of atoms present in a molecule C H that determines the characteristic CC properties of the molecule. H CC ● A homologous series is a group of compounds that contain the same HH functional group. The physical properties of a homologous series show a gradation as molecular size increases. The chemical properties of a 2 Alcohols Ethanol homologous series are similar because they are determined by the functional HH group. CO 1 Alkenes HCCO ● Alkenes contain the functional group H C=C. HH H ● Their general formula is CnH2n. ● Alkenes are reactive and undergo additional reactions. 2 Alcohols 3 Carboxylic acids Ethanoic acid ● Alcohols contain the functional group O C-OH. O ● Their general formula is CnH2n+1OH. ● Alcohols can also undergo oxidation H C to give carboxylic acids, or they can be C dehydrated to alkenes. They can also C O H react to form ester compounds O H 3 Carboxylic acids HH ● Carboxylic acids contain the functional group -COOH. ● Carboxylic acids are typically weak acids that partially dissociate into H+ cations 4 Esters Methylethanoate and RCOO- anions in aqueous solution. ● Carboxylic acids are widespread in O nature. H O 4 Esters ● Esters contain the functional group C HCC H –COOC-. mation Ltd. ● or Esters are formed by a reaction O H between a carboxylic acid and an H O CH

Alcohols CHEMISTRY OF CARBON

1 The first six alcohols Key words

Structure Name alcohol alkane CH3-OH methanol functional group hydrogen bond CH3CH2-OH ethanol

CH CH CH -OH propan-1-ol 3 2 2 1 Naming ● Alcohols are named by dropping the CH3CH2CH2CH2-OH butan-1-ol terminal “e” from the alkane chain CH3CH2CH2CH2CH2-OH pentan-1-ol and adding “ol.” For example, methane is the alkane; methanol is the CH3CH2CH2CH2CH2CH2-OH hexan-1-ol alkanol, or alcohol. When necessary, the position of the hydroxyl (-OH) group is indicated by a number between the alkane name and the “ol,” 2 Classification e.g., propan-1-ol, or in front of the H name, e.g., 2-propanol. H H H 2 Classification H H H H H H H ● Alcohols may be classified as primary, HCCOHHCCC HHCCCH secondary, or tertiary on the basis of the number of carbon atoms bonded HH HOHH HOHH to the carbon carrying the functional group (-OH).

Primary alcohol Secondary alcohol Tertiary alcohol 3 Sharing of electrons ● An oxygen atom is more electronegative than a hydrogen atom, and this leads to an unequal sharing of 3 Sharing of electrons the electrons in the O-H bond. The bonding electrons are drawn more RO␦- toward the oxygen atom and, because the electrons carry a negative charge, the oxygen atom becomes slightly ␦+ negative. This is described as delta H minus and is denoted by ␦-. Conversely, the hydrogen atom becomes slightly positive—delta plus, denoted by ␦+.(R represents the 4 Hydrogen bonding carbon group attached to the oxygen.) RO 4 Hydrogen bonding ● The -OH functional group generally makes the alcohol molecule polar. It H has a positive charge at one end and a negative at the other. Molecules can form hydrogen bonds with one another and other compounds when the oppositely charged parts are mation Ltd.

CHEMISTRY OF CARBON Carboxylic acids

Key words 1 The first six carboxylic acids

alkali pH Structure Name carbonate salt carboxylic acid CHOOH methanoic acid dissociation homologous CH3COOH ethanoic acid series

CH3CH2COOH propanoic acid 1 Naming CH3CH2CH2COOH butanoic acid ● Carboxylic acids are named by adding the suffix “anoic acid” to the prefixes CH3CH2CH2CH2COOH pentanoic acid used for all homologous series of organic compounds. For example, the CH3CH2CH2CH2CH2COOH hexanoic acid carboxylic acid containing three carbon atoms is “prop” + “anoic acid” = “propanoic acid.” 2 Hydrogen bonding 2 Hydrogen bonding ● Hydrogen bonding is present between carboxylic acid molecules, resulting in higher boiling points than might O R otherwise be expected and miscibility with water. 3 Ionization RC C O ● Carboxylic acids ionize to give hydrogen ions, H+; however, they are weak acids because they are only O H O partially ionized. ● The dissociation constant for ethanoic acid, for example, is 1.75 x 10-5 H mol3dm-6. This means that only about 4 molecules in every 1,000 are ionized at any one time.

Characteristics 3 Ionization ● Carboxylic acids have a pH value of approximately 3–5. ● Carboxylic acids react with carbonates and hydrogencarbonates to produce O O carbon dioxide: + 2- 2H (aq) + CO3 (aq) ➞ H2O(l) + CO2(g) RC RC + - H (aq) + HCO3 (aq) ➞ H2O(l) + CO2(g) ● Carboxylic acids form salts with alkalis: O O + H

CH3COOH(aq) + NaOH(aq) ➞ ethanoic acid sodium hydroxide - + CH3COO Na (aq) + H2O(l) mation Ltd. sodium ethanoate water or Visual Inf © Diagram 165

Esters CHEMISTRY OF CARBON

Key words 1 Forming esters alcohol ester O concentrated O alkyl functional group sulfuric aryl saponification acid RC RC carbon carboxylic acid OH + H OR´H2O O R´ Esters 2 Naming ● Esters contain the functional group –COOR, where R is an alkyl or an al ry Structure of ester Name of ester group.

H O 1 Forming esters ● Esters are formed by the reaction of HCC H carboxylic acids with alcohols in the methyl ethanoate presence of a strong acid catalyst, such H O C H as concentrated sulfuric acid. The reaction involves the loss of water. H ● Esters generally have a fruity smell that can be used to identify their presence. H They are used for food flavorings and O in cosmetics. ● –OH HCC HH Esters have no group, so they ethyl ethanoate cannot form hydrogen bond like O CCH carboxylic acids and alcohols. H Consequently, they are more volatile HH and are insoluble in water. 2 Naming H O ● The name of an ester is derived from the carboxylic acid and the alcohol HHCl from which it is formed. HCC propyl ethanoate ● The alcohol part of an ester is written H O CCCH at the beginning of the ester name; from methanol we get methyl, from HHH ethanol we get ethyl, etc. ● The acid part of an ester is written at H H the end of the ester name. It is written O as if it was an ionic carboxylate group in a salt; from ethanoic acid we get HCC C methyl propanoate ethanoate, from propanoic acid we get propanoate, etc. H H O CH3 3 Saponification ● When esters are heated with an alkali, such as sodium hydroxide, they are 3 Saponification readily hydrolyzed to form an alcohol and a carboxylic acid salt. ● This may be described as a O O saponification reaction. It is mation Ltd.

important in the production of soaps or RC + NaOH RC +OHR´ from fats and oils.

CHEMISTRY OF CARBON Soaps and detergents

Key words 1 Common fatty acids

carboxylic acid hydrophobic Name Formula Found in detergent soap ester palmitic acid CH3(CH2)14COOH animal and vegetable fats fatty acid hydrophilic stearic acid CH3(CH2)16COOH animal and vegetable fats

oleic acid CH (CH ) CH=CH(CH ) COOH most fats and oils Soaps and Detergents 3 2 7 2 7

● Soaps are cleansing agents made from linoleic acid CH3(CH2)4CH=CHCH2CH= soya-bean oil and nut oil fatty acids derived from natural oils CH(CH2)7COOH and fats. Detergents are made from synthetic chemical compounds. 2 Making soap 1 Fatty acids ● Carboxylic acids occur in animal and O O plant fats and oils. They may contain CH —O—C—R´ CH —OH + R´ —C—O–Na+ from 7 to 21 carbon atoms and are 2 2 often referred to as fatty acids. O O

2 Making soap – + CH —O—C—R´´ + 3NaOH CH —OH + R´´ —C—O Na ● Most naturally occurring fats and oils are esters of propane-1,2,3-triol O O (glycerine). When the fats are boiled – + with sodium hydroxide, propane1,2,3,- CH2—O—C—R´´´ CH2—OH + R´´´—C—O Na triol and a mixture of sodium salts of the three carboxylic acids are formed. 3 Soap molecule These salts are what we call soaps. H H H H H H H H H H H H H H H 3 Soap molecule O ● One end of a soap molecule is ionic, H—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C while the other end is covalent. The O–Na+ ionic end is described as hydrophilic H H H H H H H H H H H H H H H because it dissolves in water. Conversely, the covalent end is 4 Cleaning action described as hydrophobic because it does not dissolve in water, but it will water O dissolve in organic substances like oils. = water C =

4 Cleaning action O

NaO = ONa O = ● The cleaning action of soap is the C==O == C O result of the different affinities of the C == NaO C two ends of the soap molecule. ONa ● The hydrophobic end of the molecule oil ONa dissolves in oils and fats on the fabric, while the hydrophilic end of the fabric molecule remains in the water. ● The oil and fat particles are lifted off the fabric and held in the water by 5 Detergent molecule soap molecules. H H H H H H H H C—C O mation Ltd. 5 Detergent molecule or – + ● Alkylbenzene sulfonates are common H—C—C—C—C—C—C—C—C—C C—S—O Na

Organic compounds: CHEMISTRY OF CARBON states Key words alkane alkene Alkanes homologous HH series Chain length HCCH Gas C2, Physical properties ● All homologous series of compounds HH show a gradation of physical properties as the carbon chain length HHHHH increases. Alkanes Chain ● The simplest alkane is CH , methane. length Liquid 4 HCCCCCH The next simplest alkane is the two C5, carbon alkane, ethane (C2H6). Both of these are gases. HHHHH ● The five carbon alkane, pentane

(C5H12), is a liquid. ● The 34 carbon compound, butadecane HH HH is a solid. Chain Alkenes length HCC(CH) CCH Solid 2 30 ● The simplest alkene is the two carbon C34, alkene, ethene (C2H4), which is a gas. HH HH ● 2-pentene (C5H10), which is a five carbon alkene, is a liquid. ● 2-butedecane, which is a 34 carbon alkene, is a solid. HHAlkenes Chain length CC Gas C2, HH HH HH Chain length HCCCCCH Liquid C5, HHHH H H H

CHEMISTRY OF CARBON Functional groups and Key words properties alcohol functional group aldehyde homologous Class of Functional alkene series Example carboxylic acid ketone compound group ester polymer H H Functional groups and Alkene CC CC properties ● All members of an homologous series HH Ethene of compounds has the same functional group. Because the H functional group determines most of HH H the chemistry of a compound, Alcohol HCCO C O members of a particular homologous series will have similar chemical HH H Ethanole reactions. ● Alkenes are unsaturated compounds H H H because they all contain a Carboxylic carbon–carbon double bond that HCC C acid makes them very reactive. Typically, they will undergo addition reactions H OH OH with hydrogen, halogens, and water. Ethanoic acid They also form a variety of polymers. O O ● Alcohols with a small relative HC H C molecular mass are flammable liquids Ester and readily dissolve in water. Primary OCH OC alcohols are readily oxidized: first to Methyl methanoate aldehydes and then to carboxylic H acids. Secondary alcohols are oxidized Class of Typical chemical property to ketones: compound [O] [O] R-CH2-OH ➞ R-CHO ➞ Br Br R-COOH Alkene primary alcohol ➞ aldehyde ➞ CC +Br2 CC carboxylic acid HH Decolorizes bromine water [O] R-CHOH-R ➞ R-CO-R H H H H secondary alcohol ➞ ketone conc ● Carboxylic acids are weak acids since Alcohol HCCOH CC H2SO4 they only partially ionize. They have HH HH similar reactions to fully ionized Decolorizes bromine water mineral acids but they react with less vigor. Sodium salts of carboxylic acids are ionic compounds. Those with Carboxylic 2CH COOH + Na CO 2CH COO–Na+ + CO + H O short carbon chains are readily soluble acid 3 2 3 3 2 2 in water. ● Esters are volatile liquids or low- Reacts with sodium carbonate solution melting solids. They are usually mation Ltd.

or insoluble in water but soluble in ethanol and diethyl ether. Esters have HCOOH + NaOH HCOO–Na+ + CO OH Visual Inf sweet fruity smells and are used in Ester 3 3 perfumes, flavorings, and essences. Can be hydrolized by alkali © Diagram 169

Reaction summary: CHEMISTRY OF CARBON alkanes and alkenes Key words addition polymerization Alkanes alkane alkene solvent

Combustion Reaction of alkanes and alkenes C3H8 + 5O2 3CO2 + 4H2O ● Both alkanes and alkenes burn readily in a good supply of air to produce carbon dioxide and water. ● Crude oil is a complex mixture of alkanes, which are separated into Substitution fractions (components) on the basis of boiling point during the refining process. Some of these fractions CH4 + Cl2 CH3Cl + HCl provide gasoline, diesel, aviation fuel, and fuel oil. ● The quality of gasoline (how smoothly it burns) in indicated by its octane number, which ranges from 0–100: the higher the octane number the Cracking smoother burning the gasoline. The octane number is the percentage by C8H18 H2C = CH2 + C6H14 volume of 2,2,4-trimethylpentane (also known as iso-octane) in a mixture of 2,2,4-trimethylpentane and heptane, which has the same knocking characteristics as the gasoline being Alkenes tested. ● Historically, tetraethyllead(IV) Hydrogenation Pb(C2H5)4 was added to gasoline as an anti-knock additive to make it burn H C = CH + H H C – CH more smoothly. A growing knowledge 2 2 2 3 3 of the poisonous nature of lead has resulted in the development of lead- free fuels in which other anti-knock additives, such as MTBE (methyltert- Substitution butyl ether), are used. ● Crude oil contains no alkenes, but H C = CH + Br H C – CH they are produced in cracking and 2 2 2 2 2 other refining processes. Alkenes are important feedstock for addition polymerization but are also used in Br Br gasoline blending, making plasticizers, and as solvents. ● Much of the chemistry of the alkenes is the result of the reactive nature of the carbon–carbon double bond. General reaction alkene to alkane mation Ltd. Alkenes undergo addition reactions or with a variety of substances.

CHEMISTRY OF CARBON Reaction summary: Key words alcohols and acids alcohol ethene aldehyde oxidizing agent carboxylic acid Alcohols ester ethanol Preparation in industry

1 Alcohols H3PO4 at 300°C CH2 = CH2 + H2O CH3CH2OH ● The majority of the world’s annual +70 Atmospheres production of ethanol is made by the catalytic hydration of ethene. Fermentation A mixture of ethene and steam at 300°C and 70 atmospheres is passed enzyme enzyme C H O + H O 2C H O 4CH CH OH + 4CO over a phosphoric acid catalyst. 12 22 11 2 catalyst 6 12 6 catalyst 3 2 2 ● Ethanol is also made industrially by the fermentation of carbohydrates. Preparation in the laboratory ● It can also be prepared in the laboratory using concentrated sulfuric conc H SO CH = CH + H O 2 4 CH CH OH acid and heat. 2 2 2 + heat 3 2 ● Ethanol burns readily in air. In some countries it is used as a blending agent in motor fuels. Oxidation by burning ● Alcohols can be oxidized to carboxylic acids by heating with a suitable CH3CH2OH + 3O2 2CO2 + 3H2O oxidizing agent such as acidified potassium dichromate. The oxidation involves two stages and goes via a Oxidation by oxidizing agent group of compounds called aldehydes. K CR O + dil H SO Under suitable conditions, the ethanal CH CH OH 2 2 7 2 4 CH + COOH can be removed from the reaction 3 2 3 mixture before it is further oxidized to ethanoic acid. Reaction to produce an ester 2 Acids conc CH3CH2OH + CH3CO2H H2O + CH3CO2CH2CH3 ● Salts of short-chain carboxylic acids, H2SO4 like sodium ethanoate, are ionic compounds and are soluble in water. Organic acids ● Ethanoic acid and ethanol react in the presence of a concentrated sulfuric acid catalyst to form the ester ethyl Reaction giving ionic salt ethanoate. This reaction is reversed by – + heating ethyl ethanoate with an alkali CH3CO2 + NaOH CH3COO Na + H2O such as sodium hydroxide solution. The sodium salt formed, sodium ethanoate, can be neutralized by dilute mineral acid to regenerate ethanoic Reaction giving covalent ester acid. esterification CH3CO2 + CH3CH2OH CH3COOCH2CH3 + H2O ethanoic acid + ethanol ➞ ethyl ethanoate mation Ltd. hydrolysis or ethyl ethanoate ➞ Reaction giving hydrolysis of an ester

Optical isomerism CHEMISTRY OF CARBON

Key words 1 Chiral molecule chiral enantiomer W optical isomerism racemate asymmetric carbon atom

C Optical isomerism ● Optical isomerism is a form of X Z isomerism in which two isomers are the same in every way except that they Y are mirror images that cannot be superimposed on each other. 1 Chiral molecule ● When four different groups are 2 Enantioners attached to a carbon atom, the resulting molecule has no symmetry. mirror The molecule is said to be chiral, and the carbon atom at the center is Cl Cl described as asymmetric. 2 Enantiomers ● 1-bromo-1-chloroethane is a chiral C C molecule. It exists in two forms, called enantiomers, that differ only in the way that the bonds are arranged in Br H H Br space. CH3 H3C ● The enatiomers of a chiral molecule are mirror images of each other and cannot be superimposed on each rotate other. 3 Optical activity these are not Cl ● Chiral molecules are said to be the same molecule optically active since they rotate the plane of polarized light. If polarized C light is passed through a solution containing only one of the enantiomers, the plane of the light will Br CH3 be rotated either to the right (dextro- rotatory) or to the left (laevo-rotatory). H A similar solution containing only the other enantiomer will rotate the plane of the light by the same amount in the opposite direction. 3 Optical activity ● A solution containing equal amounts of the enantiomers is called a racemic Polarized dextro-rotatory or (+) rotatory mixture or racemate. It is optically light laevo-rotatory or (–) rotatory inactive since the two effects cancel mation Ltd.

CHEMISTRY OF CARBON Amino acids and proteins

Key words 1 Amino acids amine protein amino acid zwitterion carboxylic acid CH2 H functional group optical isomerism H2N—CH—COOH H2N—CH—COOH alanine glycine 1 Amino acids ● Amino acids are compounds that contain both amine (-NH2) and a NH carboxylic acid (-COOH) functional 2 groups. COOH C O ● Amino acids are generally crystalline solids that decompose on melting. They are soluble in water and CH2 CH2 insoluble in organic solvents such as ethanol. H2N—CH—COOH H2N—CH—COOH aspartic acid asparagine 2 Alanine ● Like most ␣-amino acids, alanine contains an asymmetric carbon atom 2 Alanine and exhibits optical isomerism. There are two forms of alanine; L-alanine and D-alanine (L=laevo-[left] rotatory; D=dextro-[right] rotatory.) CH3 CH3 3 Zwitterions ● In aqueous solution, amino acids are C COOH C H able to form ions that carry both positive and negative charge. Such ions are called zwitterions. They form H2N H2N by the loss of a proton from the carboxylic acid group and the gain of a H COOH proton on the amine group. L-alanine D-alanine 4 Proteins ● Proteins are polymers consisting of long chains of amino acids. The amino 3 Zwitterions acids join together forming peptide bonds by the loss of water: R R -H2O + H N-CHR-COOH + H N-CHR-COOH ➞ – 2 2 H2N—CH—COOH H2N—CH—COO H2N-CHR-CONH-CHR-COOH ● All of the amino acids in proteins are the L-isomers. 4 Proteins

R O R mation Ltd. —H2N—CH—C or HN—CH—C

Monosaccharides CHEMISTRY OF CARBON

Key words 1 Chain structure aldehyde hexose 1 1 aldohexose monosaccharide CHO CHO aldose anomer H—2C—OH HO—2C—H glucose 3 3 HO— C—H H— C—OH Monosaccharides 4 4 ● Monosaccharides are simple sugars H— C—OH HO— C—H that have between three and six carbon atoms. Those with six carbon 5 5 H— C—OH HO— C—H atoms are known as the hexoses and have the general formula C6H12O6. 6 6 CH OH CH OH ● Monosaccharides with an aldehyde 2 2 group (-CHO) are called aldoses. ● Glucose has both an aldehyde group D-glucose L-glucose and six carbon atoms and is therefore an aldohexose.

2 Ring structure 1 Chain structure ● For simplicity, monosaccharides are 66sometimes displayed as vertical open -H CH2OH CH2OH chain structures to which the and –OH groups are attached. C O C O ● Aldohexoses contain four H 55H HOHasymmetrical carbon atoms: C-2, C-3, C-4, and C-5. There are 8 different H H possible ways of arranging the –H and C H C C H C –OH groups on these carbon atoms, 4411 OH OH and each of these has two optical OH OH OH H isomers, making a total of 16. CC2 CC2 ● The most important of these are the 3 3 two optical isomers of glucose. H OH H OH ● For glucose the D- and L- indicate the configuration of the –H and –OH α-D-glucose β-D-glucose groups on C-5. 2 Ring structure ● In reality, solid monsaccharides do not 3 Hexagonal ring exist as open chain structures but as ring structures. 6 O ● In Howarth projections of H CH2OH monosaccharides, groups are shown on vertical bonds above and below a H flat hexagonal ring. 4 5 ● D-glucose can exist in two separate HO 2 OH crystalline forms known and ␣-D- H glucose and ␤-D-glucose. These forms are known as anomers. HO 3 OH 1 3 Hexagonal ring mation Ltd. or H ● The hexagonal ring in a

CHEMISTRY OF CARBON Disaccharides and Key words polysaccharides cellulose polysaccharide disaccharide starch glycogen sucrose 1 Sucrose monosaccharide

Di-and polysaccharides ● A disaccharide is formed when two monosaccharides join together. A H O CH2OH molecule of water is lost and a glycosidic link is formed. ● A polysaccharide is a polymer formed HO H CH2OH O H by the joining of many H H monosaccharide units. HO H HO 1 Sucrose OH CH2OH ● Sucrose, the sugar widely used on foods, is a disaccharide. H O HO H 2 Cellulose ● Cellulose, a polysaccharide, provides plant cells with a rigid structure. glycosidic bond 3 Starch ● Glycogen is the storage polysaccharide of animals. ● Starch is the storage polysaccharide of plants.

2 Cellulose

CH2OH H OH CH2OH H OH O O H O H H O H H OH H OH H H H H OH H OH H O O H H H H O O

H OH CH2OH H OH CH2OH

3 Starch CH2OH CH2OH CH2OH CH2OH O O O O HHHHHHH H H H H H H H H mation Ltd. OH OH OH OH or O OOO Visual Inf H OH H OH H OH H OH © Diagram 175

Ionizing radiation RADIOACTIVITY

Key words 1 Alpha particles alpha particle proton beta particle gamma radiation ionizing radiation α-radiation consists Produces intense of a stream of α ionization in a particles gas Ionizing radiation neutron ● Ionizing radiation is any radiation capable of displacing electrons from atoms or molecules and so producing ions. Examples include alpha 2 Beta particles particles, beta particles, and gamma radiation.

Produces less 1 Alpha particles β-radiation consists electron intense ● An alpha (␣) particle has the same of a stream of β – ionization in a particles gas than a structure as a helium nucleus (two particles protons and two neutrons). ● Alpha particles are relatively heavy, high-energy particles with a positive charge. 3 Gamma radiation ● Alpha particles produce intense ionization in a gas. ● Emission speeds are typically of the order of 5–7 percent of the speed of light. γ-radiation is a form Only weakly of electromagnetic ionizes a gas radiation 2 Beta particles ● A beta (␤ ) particle is a fast-moving –12 Wavelength <10 m electron with a negative charge. Frequency >1021 Hz ● Beta particles produce less ionization in a gas than alpha particles and on average produce only 1/1000th as 4 Radiation in laboratories many ions per unit length. ● Emission speeds can be as high as 99 percent of the speed of light. 3 Gamma radiation ● Gamma (␥) rays ionize gas only weakly and on average produce only 1/1000th lead container as many ions per unit length as beta particles. 4 Radiation in laboratories 4 mm ● Sources of radiation used for plug laboratory experiments are usually supplied mounted in a holder. The active material is sealed in metal foil, active metal foil which is protected by a wire gauze mation Ltd.

© Diagram Visual Information Ltd. ● 4 ● GM 3 ● 2 ● ● 1 ● Detectors radioactivity radiation ionizing radiation Key words track whenilluminated. liquid dropletsthatshowsupasa period whenthe materialisremoved. minute withthecountover same GM tubeandcomparingthecount per between aradioactivesourceand a be testedbyplacingthematerial alpha, beta,andgammaradiation can The abilityofmaterialstoabsorb produce acur reaching theelectrodes,ions collide withotherargonatoms.On accelerated towardtheelectrodesand ions andelectrons.Theseare through thetubewall,itcreatesargon either throughthemicawindowor When air ionizing radiation cooled, itbecomessaturated.If When aircontainingethanolvaporis intervals. are seenandheardatir and thegauzeisionized,sparks the gauze,airbetweenwire When aradiumsourceisbroughtnear stops sparking. (cathode) andreduceduntilitjust stiff wire(anode)andthegauze High voltageisappliedbetweenthe variety ofmethods. scientists caneasilydetectitusinga it affectstheatomsthatpasses, Radioactivity air condense ontheionscreatedin counter. amplified beforebeingfedtoapulse Spark counter Cloud chamber Testing absorption . coolingcausesthevaporto , further

The resultisawhitelineoftiny radiation tube RADIOACTIVITY rent pulse,whichis is invisible,butbecause 176 enters themetaltube, passes throughthis regular

Radiation detectors i h g f e d c b a (GM tube) 3 Geiger-Muller tube 2Cloudchamber 1 Spark counter super-cooled vapor chamber circular transparent plastic E.h.t. supply insulating base forceps radium source wire gauze (cathode) sparks stiff wire (anode) q a b f u r + – g s – – – + – – w – – – t v r q p o n m l k j argon gas at low pressure mica window black metal base plate crushed dryice foam sponge radioactive source base and water felt strip soaked with alcohol transparent lid d e c h radiation alpha, beta, and gamma 4 Testingabsorbtion of

a i o x a z y x w v u t s aa aa m n GM tube absorbing material source avalanche the anodewire inan electrons are pulledtoward pulse counter cathode metal tube insulator anode wire y + –

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a l

a a p a k 177

Properties of radiations: RADIOACTIVITY penetration and range Key words alpha particle beta particle 1 Penetration of radiation 2 Range of radiation in air gamma radiation radiation

d e h a 1 Penetration

f ● Alpha, beta, and gamma radiation penetrate by different amounts. i ● Alpha radiation is the least penetrating b and is stopped by a sheet of paper or very thin metal foil. g ● Beta radiation is stopped by aluminum a few millimeters thick. c k ● Gamma radiation is most penetrating, and is only stopped by a thick block of lead. j 2 Range ● The penetrating power of alpha, beta, and gamma radiation is reflected in the distance that they can travel 1mm 3mm 1cm 1cm 1m 2m 3m through air. Alpha particles can only travel a few centimeters before a α – source e paper h α – a few centimeters colliding with air particles. Beta b β – source f aluminum i β – a few meters particles travels a few meters, while c γ – source g lead j γ – many meters gamma radiation can travel many d metal foil k area covered by γ radiation at 1m distances meters. 3 Gamma penetration 3 The inverse square law for gamma radiation penetration ● Gamma rays are highly penetrating y because they have relatively little interaction with matter. There is very + little absorption or scattering as they pass through air. ● The intensity falls off with distance according to the inverse square law: + I = k d2 I d e + where is intensity, is the distance t a

r from the source, and k is a constant. t

n At a distance x, the intensity of the u o

C gamma radiation: + Ix = k x2 At a distance 2x, the intensity of the gamma radiation: + I2x = k = k (2x)2 4x2 mation Ltd.

As the distance increases by a factor of or + 2, the intensity of the gamma radiation

decreases by a factor of 4. Visual Inf 0 10 50 100 150 200 250 x 1 d2 © Diagram © Diagram Visual Information Ltd. ● ● ● 2 ● ● ● 1 ● ● fields Electric andmagnetic gamma radiation electric field beta particle alpha particle Key words to alphapar electric fieldintheoppositedirection a have greater becausethebetaparticles radiation carries nocharge. radiation carries magnetic field,indicatingthat gamma Gamma radiationisnotdeflected bya carr its particles direction toalpharadiation,indicating radiation isdeflectedintheopposite relatively weakmagneticfield.Beta Beta radiationisdeflectedbya compared tobetaparticles. greater massofalphaparticles have nonoticeableeffectduetothe magnetic field.Weak magneticfields Alpha radiationisdeflectedbyastrong gamma radiationcar an electricfield.Thisisevidencethat Gamma radiation of Astream negatively chargedparticles. Beta radiationiscomposedof plates. Thepar between twooppositelycharged passing throughtheelectricfield of Astream positively chargedparticles. Alpha radiationiscomposedof differently inboth. beta, andgammaradiationbehave conductor.current-carrying Alpha, exists aroundamagneticbodyor A An charged plate. attracted towardthenegatively the positivelychargedplateand charged par outward inalldirectionsfroma Electric field Magnetic field much smallermass. magnetic fieldisanareaofforcethat beta particles alpha particles electric field RADIOACTIVITY ticle. ticles. Thedeflectionis ticles arerepelledfrom 178 y is afieldextending is deflectedbyan an oppositecharge. is deflectedwhen is notdeflectedby ries nocharge. in fields Properties ofradiations: aito 1Electric field Radiation Gamma Beta Alpha – + – + – + 2 Magnetic field N N N S S S magnet magnet magnet 179

Stable and unstable RADIOACTIVITY isotopes Key words isotope 130 nucleon nuclide

120 Stability ● The stability of isotopes is based on the ratio of neutrons and protons in their 110 nucleus. Although most nuclei are stable, some are not and Unstable region spontaneously decay, emitting radiation. 100 ● The lightest stable nuclides (particular isotopes of an element) have almost equal numbers of protons and neutrons. The heavier stable nuclides 90 require more neutrons than protons. The heaviest stable nuclides have approximately 50 percent more 80 neutrons than protons. Odd-even rule ● Isotopes tend to be more stable when N s

n 70 they have even numbers of protons o r

t and neutrons than when they have u

e band of stability

n odd. This is the result of the spins of f

o the nucleons (the constituents of the

r N = Z e atomic nucleus). When two protons or b 60

m neutrons have paired spins (spins in u

N opposite directions), their combined energy is less than when they are 50 unpaired. Decay ● When unstable nuclides disintegrate, 40 they tend to produce new nuclides that are nearer to the stability line. This will continue until a stable nuclide is formed. 30 ● An unstable nuclide above the band of Unstable region stability decays by beta emission. This increases the proton number and decreases the neutron number. Thus, 20 the neutron to proton ratio is decreased. ● An unstable nuclide below the band of stability disintegrates so as to decrease 10 the proton number and increase the mation Ltd.

neutron to proton ratio. In heavy or nuclides this can occur by alpha

emission. Visual Inf 0 010 20 30 40 50 60 70 80 90 Number of protons (Z) © Diagram © Diagram Visual Information Ltd. ● ● ● 2 ● ● 1 nuclide isotope half-life alpha particle Key words law equationfor Substituting thisintotheexponential radioactive atom: decay constantandthehalflifeofa mathematical relationshipbetweenthe logs ofbothsidesprovidesa After onehalflife( number ofnuclei, tothe time isdirectlyproportional The rateofdecayanuclideatany active There arealwaysver temperature andpressure. factorssuchas other orexternal disintegrate independentlyofeach random processinwhichnuclei decayisacompletely Radioactive undergo the nucleiinasampleofan Half-life remaining inthesamplewillbe number ofundecayedatoms average, overagivenperiodoftime. the fractionthatwillhavedecayed,on methods canbeemployedtopredict of radioactivematerial,sostatistical of undecayed atoms after time of undecayedatomsafter atoms attime where where law equation: Integrating thisgivestheexponential of undecayednucleifallswithtime. minus signindicatesthatthenumber nuclei and t N -dN Half-life (1/2) dt Rate ofdecay t N = ϰ = nuclides 0 N N N 0.693 e RADIOACTIVITY 0 -␭t is thetimerequiredforhalf or dN=- is thenumberofundecayed radioactive decay ␭ is thenumberofundecayed ␭ is thedecayconstant.The 0 = t 180 even insmallamounts N ␭ t N t N 1/2 and takingnatural and , y of thenuclide: ) large numbersof has passed,the N t the number . isotope t . N 0 /2 to . Half-life

Number of undecayed nuclei, N 2 1 Half-life Rate of decay N N N N 8 4 2 0 0 0 0 N 0 Half-life Typical ra flf H Half-life dioactive decay c N 2 0 urve alf-l f T ife N 4 0 ime, t 181

Measuring half-life RADIOACTIVITY

Key words 1 Half-life of radon alpha particle e a i half-life b isotope

1 Half-life of radon ● Thorium decays to produce the f radioactive isotope radon-220. This isotope is sometimes referred to as c thoron. + ● The bottle containing thorium hydroxide powder is squeezed a few g times to transfer some radon-220 to – the flask. The clips are then closed. d ● As the radon decays, the ionization h A current decreases. It is always a measure of the number of alpha particles present and, therefore, the proportion of radon-220 remaining. a ionization chamber f valves b air g squeezable polyethylene ● The current is noted every 15 seconds c radon bottle for 2 minutes and then every 60 d d.c. amplifier h thorium hydroxide powder seconds for several minutes. e clips i clock 2 Exponential decay 2 Exponential decay: decay curve for radon gas ● A graph of current against time is plotted. y ● In this experiment, the half-life is 1.0 indicated by the amount of time taken for the current to fall to half of its original value. ● The half-life of radon-220 is approximately 55 seconds. ) s p 3 Radon decay m a ( 0.5 ● Radon-220 decays with the loss of an t n

e alpha particle to form polonium-216, r r

u which decays to form lead-212. The C 0.25 half life of polonium-216 is 0.145 seconds, and the half life of lead-212 is 0.125 10.64 hours.

0 0 50 100 150 200 x Time (s)

3 Radon decay

Ra-222 Po-216 Pb-212 mation Ltd. or Visual Inf © Diagram © Diagram Visual Information Ltd. ● 6 ● 5 ● 4 ● 3 ● 2 ● 1 isotope irradiation gamma radiation alpha particle Key words isotope throughtheplant. used todetectthemovementof stem ofaplant.AGeigercounteris to saywhenanorganismdied. carbon-14 tocarbon-12,itispossible 5,700 years.Bycomparingthe ratio of at apredictablerate:thehalf-life is is When anorganismdies,nocarbon-14 radioactive carbon-14tocarbon-12. All organismscontainaspecificratioof triggers analarm. which cause achangeinthecurrent, detectors. The radiation, iswidelyusedinsmoke Americium-241, asourceofalpha medical equipment. Gamma radiationisusedtosterilize shelf lifeoffoodisextended. well asthosethatspoilfood,sothe destroys disease-causingbacteriaas gamma radiation Food byexposingitto isirradiated isotope andmonitorthyroidactivity. Geiger counterisusedtodetectthe patient withadefectivethyroid.A introduced tothebloodstreamofa A phosphor solution containingradioactive substances inplantsandanimals.A to monitorthemovementof Radioactive smok the airinsensingcircuit.Any Tracers Food preservation Smoke detectors Thyroid monitor Duration ofdeath Sterilization solution containingiodine-131is added. Afterdeath,carbon-14decays e particles interfere withthisand interfere e particles RADIOACTIVITY us-32 isintroducedintothe isotopes alpha particles 182 . Irradiation are usedastracers ionize Radioactive isotopes 3 1 5 gamma Tracers Food preservation Smoke detectors rays current electric circuit current-sensing battery bacteria dying Carbon-12 4 2 6 constant Thyroid monitor Duration of death Sterilization medical equipment Grasshopper organism Dead gamma rays Carbon-14 decreases 183

Nuclear fusion RADIOACTIVITY

Key words 1 Nuclear fusion fusion proton proton isotope

proton proton

1 Nuclear fusion ● In nuclear fusion, two or more light atomic nuclei join to make a more massive one. During the process, some of the mass of the nuclei is helium converted into energy. Nuclear fusion, nucleus which first occurred during the Big Bang, powers stars. It also occurs in hydrogen bombs. Currently scientists are working to control fusion so it can positron positron be used in nuclear reactors. electron electron 2 Deuterium ● Deuterium is an isotope of hydrogen starlight known as heavy hydrogen. The nucleus of a deuterium atom consists of one neutron and one proton. ● The fusion of two deuterium nuclei results in the formation of a helium-3 nucleus. A small amount of mass is 2 Fusion of deuterium converted into energy: Mass of two deuterium nuclei = 2 x 2.014 = 4.028 u Mass of helium-3 nucleus plus a neutron = 3.016 + 1.009 = 4.025 u Mass converted to energy by fusion = 4.028 – 4.025 = 0.003 u 2 H 2 H 3 He 1 n Energy released by the fusion reaction 1 1 2 0 = 4.5 x 10-13 J deuterium deuterium helium-3 neutron Energy released per kilogram of deuterium is approximately 9 x 1013 J. 3 Tritium ● 3 Fusion of deuterium and tritium Tritium is another isotope of hydrogen. The nucleus of a tritium atom consists of two neutrons and one proton. ● The fusion of a deuterium nucleus and a tritium nucleus results in the formation of a helium-4 nucleus and the release of energy. The energy released per kilogram of deuterium mation Ltd.

and tritium is approximately or 2 3 4 1 30 x 1013 J. 1 H 1 H 2 He 0 n ● deuterium tritium helium-4 neutron This reaction produces more energy, Visual Inf and the fusion takes place at a lower temperature. © Diagram © Diagram Visual Information Ltd. ● ● ● ● 2 ● 1 ● Nuclear fission fission chain reaction Key words rapidly broughttogether. uranium-235 (orplutonium-239)are other nuclei. trigger thefissionofatleastasmany par process. intoenergyduringthe converted ones. Someofthemassnucleiis reactions. fission neutrons bringaboutfurther only alimitednumberoffission reaction issteadyandcontrolled,so In anuclearpowerstation,thechain a uncontrolled chainreactionoccursin In anatomicbomb,increasing can start. radioactive isotope,achainreaction there isasufficientamountof neutrons actinthisway. However, if very circumstances,onlya Under normal self nuclear A toenergy.mass isconverted three neutrons.Asmallamountof (lanthanum-148 andbromine-85)plus twosmallernuclei fission andforms the uranium-235atomundergoes slow-moving neutrons,thenucleusof In anuclearreactionwithuraniumand nucleus dividestomak In nuclearfission Reaction withuranium Chain reaction ver ticles releasedbyonenucleus -sustaining reactionsinwhichthe small proportion offission small proportion y short timewhentwopiecesof short RADIOACTIVITY chain reaction 184 a , heavy atomic e twosmaller is aseriesof Nuclear fission 1 o 1 2 neutron enurnlnhnm18bromine-85 lanthanum-148 ne neutron Reaction withuranium N Chain reaction N 0 1 n +++ u ranium-235 235 92 U 3 neutrons N N N 148 57 La 85 35 r3 Br three neutrons 9 neutrons N N N 0 1 N N N N N N N N N n 185

Nuclear reactor RADIOACTIVITY

concrete sheild cooling water Key words converted to fission steam, which drives turbine isotope uranium

Nuclear reactor ● Uranium, either the metal or the metal oxide, is used as fuel in nuclear reactors. The fuel is in the form of fuel rods, which are suspended in the reactor. ● Naturally occurring uranium contains 99.3 percent uranium-238 and only 0.7 percent of the radioactive isotope uranium-235. The uranium-235 content must be increased to approximately 3 percent before the uranium can be use as a fuel. ● Uranium-235 undergoes spontaneous fission . However, in a nuclear power station, the fission is brought about by bombarding the uranium nuclei with atoms splitting inside carbon dioxide gas carries neutrons. core of the reactor heat away from uranium in ● The fission of one atom of uranium- give off heat the core of the reactor 235 absorbs one neutron and releases three others. In order to increase the chances that these neutrons will strike generator other uranium-235 atoms, they are slowed down by a moderator. cooling water ● Control rods are suspended between turbine the fuel rods. These can be raised or lowered as needed to control the nuclear reaction. The control rods are made of alloys that absorb neutrons. When they are lowered, more neutrons are absorbed. electricity ● The heat produced by the fission reaction is removed through a heat exchanger. The loop between the nuclear reactor and the heat exchanger is sealed so there is no danger of radioactive material escaping into the environment. ● The heat is used to convert water into pressurized steam. The high pressure steam drives a turbine connected to a generator, which produces electricity. cooling tower mation Ltd. or Visual Inf © Diagram © Diagram Visual Information Ltd. Pb-206 (stable) Ti-210 At-218 Th-230 U-238 Decay chain ● ● The uraniumseries ● ● Radioactive decay half-life daughter nucleus beta particle atomic number alpha particle Key words equivalent to each memberoftheserieshasamass (␤) (␣) Each diagonallinerepresentsanalpha element isatthetopofgraph. on they thex-axis.The on numbers occurs. Atomic The graphindicateshowthedecay series (where Pb-206. Itisalsoknownasthe radioactive decayofU-238tostable The uraniumseriesinvolvesthe isotope oflead. thorium series.Eachendswithastable series, radioactive decayseries:the There arethreenaturallyoccurring beta disintegrate, theyemit nuclide isproduced.Asthenuclei the of radioactive decayseries,eachmember in ordertobecomemorestable.Ina process knownas nucleibreakdown by a Radioactive and seconds(s). (a), days(d),hours(h),minutes(m), nucleus). produced bythedecayofprevious daughter nucleus . Acircleindicatesthe the seriesisfor decay decay; eachhorizontallineabeta nuclide ➞ ➞ (␤) ➞ ➞ the actiniumseries,and Th-234 Pb-210 Pb-214 -axis. Thesymbolforthe RADIOACTIVITY Ra-226 Ra-226 particles Half-life before ituntilastable 4n+2 n ➞ ➞ ➞ 186 ➞ is aninteger),because Pa-234 Bi-210 Bi-214 . med bythedecayof Rn-222 mass numbers radioactive decay (the nucleus is indicatedinyears . uranium series uranium radioactive decay nuclide mass number alpha ➞ ➞ ➞ ➞ are plotted Po-210 U-234 Po-214 Po-218 uranium (␣) 4n+2 ➞ or are ➞ ➞ ➞

Mass number The uraniumseries 200 205 220 230 240 225 235 210 215 088 80 19.7m 81 lP iP tR rR cT aU Pa Th Ac Ra Fr Rn At Po Bi Pb Tl 5 1.32m 4.2m .0d 26.8m 8 .5 1.5s 3.05m 2 2 5.0d 22a 83 138.3d 1.6 × 84 19.7m 10 –4 85 3.05m s Atomic number 3.82d 86 8 7 1620a α 89 β 8.0 24.1d 4.5 09 92 91 90 × 10 × 4 10 a 2 9 .5 × a 1.18m 10 5 a 187

The actinium series RADIOACTIVITY

Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Key words 240 actinium daughter nucleus actinium series half-life alpha particle mass number atomic number nuclide beta particle radioactive decay

235 Radioactive decay ● Radioactive nuclei break down by a 7.1 × 108a process known as radioactive decay in order to become more stable. In a 24.6h radioactive decay series, each member of the series is formed by the decay of the nuclide before it until a stable 230 nuclide is produced. As the nuclei 4 3.43 × 10 a disintegrate, they emit alpha (␣) or beta (␤) particles. 22.0a ● There are three naturally occurring radioactive decay series: the uranium series, the actinium series, and the 225 22.0a 18.6d thorium series. Each ends with a stable isotope of lead. The actinium series 21m ● The actinium series involves the r

e radioactive decay of U-235 to stable b 11.2d 4n+3 m Pb-207. It is also known as the u

n 220 series (where n is an integer), because s s

a each member of the series has a mass M equivalent to 4n+3. ● The graph indicates how the decay 3.92s occurs. Atomic numbers are plotted 1.83 × 10–3s on the x-axis. The mass numbers are 215 on the y-axis. The symbol for the element is at the top of the graph. 10–4s Each diagonal line represents an alpha (␣) decay; each horizontal line a beta 2.16m (␤) decay. A circle indicates the daughter nucleus (the nucleus produced by the decay of the previous 210 36.1m nucleus). Half-life is indicated in years α (a), days (d), hours (h), minutes (m), 0.52s 2.16m and seconds (s). Decay chain 4.2m β U-235 ➞ Th-231 ➞ Pa-231 ➞ Ac-227 ➞ ➞ ➞ ➞ ➞ 205 Th-227 Fr-223 Ra-223 Rn-219 Po-215 ➞ At-215 ➞ Pb-211 ➞ Bi-211 ➞ Po-211 ➞ Tl-207 ➞ Pb-207 (stable) mation Ltd. or Visual Inf 200 8081 82 83 84 85 86 87 88 89 90 91 92

Atomic number © Diagram © Diagram Visual Information Ltd. Pb-208 (stable) Bi-212 Ra-224 Th-232 Decay chain ● ● The thoriumseries ● ● Radioactive decay half-life daughter nucleus beta particle atomic number alpha particle Key words equivalent to each memberoftheserieshasamass series (where (␤) (␣) Each diagonallinerepresentsanalpha element isatthetopofgraph. on they thex-axis.The on occurs. The graphindicateshowthedecay Pb-208. Itisalsoknownasthe( radioactive decayofTh-232tostable The thoriumseriesinvolvesthe isotope oflead. thorium series. series, theactiniumand radioactive decayseries:theuranium There arethreenaturallyoccurring beta disintegrate, theyemit nuclide isproduced.Asthenuclei the of radioactive decayseries,eachmember in ordertobecomemorestable.Ina process knownas nucleibreakdown by a Radioactive and seconds(s). (a), days(d),hours(h),minutes(m), nucleus). produced bythedecayofprevious daughter nucleus . Acircleindicatesthe the seriesisfor decay decay; eachhorizontallineabeta nuclide (␤) ➞ ➞ ➞ Po-212 Atomic numbers Atomic Rn-220 -axis. Thesymbolforthe RADIOACTIVITY Ra-228 Ra-228 particles Half-life before ituntilastable 4n n ➞ 188 ➞ ➞ Each endswithastable is aninteger)because . Tl-208 . med bythedecayof Po-216 Ac-228 mass numbers radioactive decay (the nucleus is indicatedinyears thorium series thorium radioactive decay nuclide mass number alpha ➞ are plotted ➞ ➞ Pb-212 Th-228 (␣) 4n or are ) ➞ ➞

Mass number The thoriumseries 200 205 220 230 240 225 235 210 215 088 80 81 lP iP tR rR cT aU Pa Th Ac Ra Fr Rn At Po Bi Pb Tl 47m 3.1m 10.6h 8 2 8 3 3.0 3.0 47m 0.16s × 8 10 4 –7 s 8 5 Atomic number 54.5s 86 8 7 1.39 1.39 3.64d × 6.7a 10 10 α a 89 β 6.13h 1.90a 09 92 91 90 189

The neptunium series RADIOACTIVITY

Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Key words alpha particle mass number atomic number neptunium 245 beta particle neptunium series daughter nucleus nuclide half-life radioactive decay

Pu Am Radioactive decay 240 ● Radioactive nuclei break down by a process known as radioactive decay in order to become more stable. In a U Np radioactive decay series, each member of the series is formed by the decay of the nuclide before it until a stable 235 nuclide is produced. As the nuclei disintegrate, they emit alpha (␣) or Pa U beta (␤) particles. ● The neptunium series is composed of isotopes that do not occur in nature. 230 Th The neptunium series ● The neptunium series starts with the artificial isotope plutonium-241 and ends with bismuth-209. Each member of the series has a mass equivalent to

r Ra Ac 225 4n+1 n e (where is an integer). b

m ● The graph indicates how the decay u n occurs. Atomic numbers are plotted s s

a on the x-axis. The mass numbers are M Fr on the y-axis. The symbol of the 220 element is at the top of the graph. Each diagonal line represents an alpha (␣) decay; each horizontal line a beta (␤) decay. A circle indicates the At daughter nucleus (the nucleus produced by the decay of the previous 215 nucleus).

Bi Po Decay chain Pu-241 ➞ Am-241 ➞ Np-237 ➞ Pa-233 ➞ U-233 ➞ Th-229 ➞ Ra-225 ➞ Ac-225 ➞ α Fr-221 ➞ At-217 ➞ Bi-213 ➞ Po-213 ➞ 210 Pb-209 ➞ Bi-209 (stable) Tl Pb Bi

205 mation Ltd. or Visual Inf 200 8081 82 83 84 85 86 87 88 89 90 91 92 93 94 95

Atomic number © Diagram © Diagram Visual Information Ltd. ● ● ● 4 ● ● ● 3 ● ● ● 2 ● ● ● ● 1 beta particle beta decay atomic number alpha particle alpha decay Key words p the nucleusofanatomemits gamma radiation. The remainingenergyisreleased as beta particle. kinetic energy Some energyisreleasedinthe for nucleus. ground stateoftheprotractinium nuclide The groundstateofthethorium half-life forthisdecayis6.75hours. The 234 bythelossofabetaparticle. Thorium-234 decaystoprotactinium- The newatom’satomicnumber( par nucleus ofanatomemitsa Beta decay gamma radiation. The remainingenergyisreleasedas kinetic energy of Some energyisreleasedintheform thorium nucleus. energy thanthegroundstateof energy ofthenucleus)isatahigher nucleus (thenaturalstateofthelowest The radiation Energy isalsoreleasedas the lossofanalphaparticle. Uranium-238 decaystothorium-234by The newatom’satomicmassnumber Alpha decay number ( increased by1,whiletheatomicmass as thehelium-4nucleus: alpha particle. ( number Alpha decay A Beta decay Alpha particlespectrum article Beta particlespectrum ) ticle is reducedby4andits ground state RADIOACTIVITY is atahigherenergythanthe (an electron). (which hasthesamestructure ( A Z . ) ) is theprocessinwhich remains unchanged. is decreasedby2. is , , 190 which is carried bythe which iscarried the processinwhich which iscar of theuranium nuclide mass number kinetic energy ground state gamma radiation 2 4 He). gamma atomic beta ried bythe alpha Z m (␥) ) is of sequences Radioactivity ofdecay a b c d nuclide excited states of excited states of ground state of 4 3 2 1 Example of beta decay: thoriumdecay to protactinium General sequence of beta decay Example of alphadecay: uranium decay to thorium General sequence of alphadecay Alpha decay Beta decay Alpha particle spectrum Alpha particle Beta spectrum particle 3 A Z+1 234 Z AA 4 234 238 ZZ–22AA–44 091 90 2 90 92 c h b a d g i z hP e + Pa Th UTh+He XY+e XY+He Z Z Z – ␥ – – ␤ 2 2 2 ␥ ␣␣ j l ␤ ␤ ␣ ␣ e f g f e h nuclide gamma radiation energyalpha particle excited state of f ␣␣ ␥ Z ~ ␯ ␤ ␥ e e k j l Z + 1 ␥ l k j i ~ ␯ ␤ - - gamma radiation neutrino energy beta energy particle ground state of e k j l + + + + Z ␯~ ␯~ ␥ ␥ + 1 191

Table of naturally RADIOACTIVITY occurring isotopes 1 Key words atomic mass atomic number Table of masses and abundance of naturally occurring isotopes isotope mass number Atomic Element Symbol Mass Percentage Atomic number number mass (Z) (A) Atomic number 0 Neutron n 1 — 1.008665 ● The atomic number (Z) of an element 1 Hydrogen H 1 99.99 1.007825 is the number of protons in the 2 0.01 2.014102 nucleus of one atom of that element. 2 Helium He 3 1.3 × 10–1 3.016030 All atoms of the same element have 4 100 4.002604 the same atomic number. 3 Lithium Li 6 7.4 6.015126 7 92.6 7.016005 Element 4 Beryllium Be 9 100 9.012186 ● “Element” refers to the common name 5 Boron B 10 19.6 10.012939 11 80.4 11.009305 of the element. This list is restricted to 6 Carbon C 12 98.9 12.000000 the 89 naturally occurring elements. 13 1.1 13.003354 7 Nitrogen N 14 99.6 14.003074 Symbol 15 0.4 15.000108 ● “Symbol” refers to the shorthand form 8 Oxygen O 16 99.76 15.994915 of the element’s name used in 17 0.04 16.999133 chemical equations. 18 0.20 17.999160 9 Fluorine F 19 100 18.998405 Mass number 10 Neon Ne 20 90.9 19.992440 ● The mass number (A) represents the 21 0.3 20.993849 number of protons or neutrons in the 22 8.8 21.991384 11 Sodium Na 23 100 22.989773 nucleus of one atom of that element. 12 Magnesium Mg 24 78.8 23.985045 Not all atoms of the same element 25 10.2 24.985840 have the same mass number. Atoms of 26 11.1 25.982591 an element that have different mass 13 Aluminum Al 27 199 26.981535 numbers are called isotopes. 14 Silicon Si 28 92.2 27.976927 29 4.7 28.976491 Percentage 30 3.1 29.973761 ● “Percentage” refers to isotopic 15 Phosphorus P 31 100 30.973763 abundance. For example, 99.99 16 Sulfur S 32 95.0 31.972074 percent of naturally-occurring 33 0.8 32.971460 hydrogen has the mass number 1. 34 4.2 33.967864 36 0.01 35.967091 Only 0.01 percent has the mass 17 Chlorine Cl 35 75.5 34.968854 number 2. 37 24.5 36.965895 18 Argon Ar 36 0.34 35.967548 Atomic mass 38 0.06 37.962724 ● “Atomic mass” refers to the average 40* 99.6 30.962384 atomic mass of that element's isotope 19 Potassium K 39 93.1 38.963714 weighted by isotopic abundance. 40 0.012 39.964008 41 6.9 49.961835 20 Calcium Ca 40 97.0 39.962589 42 0.6 41.958628 43 0.1 42.958780

44 2.1 43.955490 mation Ltd.

46 0.003 45.953689 or 48 0.2 47.952519

21 Scandium Sc 45 100 44.955919 Visual Inf

*denotes radioactive isotope © Diagram © Diagram Visual Information Ltd. ● Atomic mass ● Percentage ● Mass number ● Symbol ● Element ● Atomic number mass number isotope atomic number atomic mass Key words weighted byisotopicabundance. atomic massofthatelement'sisotope numbers arecalledisotopes an elementthathavedifferentmass Atomic mass “Atomic number 2. Only 0.01percenthasthemass hydrogen hasthemassnumber1. percent ofnaturally abundance. For example,99.99 “Percentage” referstoisotopic have thesamemassnumber Not allatomsofthesameelement nucleus ofoneatomthatelement. number ofprotonsorneutronsinthe The chemical equations. of form “Symbol” referstotheshorthand elements. the 89naturallyoccurring of theelement.Thislistisrestrictedto “Element” referstothecommonname the sameatomicnumber All atomsofthesameelementhave nucleus ofoneatomthatelement. is thenumberofprotonsin The the element’snameusedin mass number atomic number RADIOACTIVITY ” 192 refers totheaverage (A) representsthe -occurring (Z) ofanelement . . . Atoms of * occurring isotopes2 Table ofnaturally denotes radioactive isotope 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 Table of masses andabundance of naturally occurring isotopes (Z) number Atomic Krypton Bromine Selenium Arsenic Germanium Gallium Zinc Copper Nickel Cobalt Iron Manganese Chromium Vanadium Titanium lmn yblMass Symbol Element Kr Br Se As Ge Ga Zn Cu Ni Co Fe M Cr V Ti 86 84 83 82 80 78 81 79 82 80 78 77 76 74 75 76 74 73 72 70 71 69 70 68 67 66 64 65 63 64 62 61 60 58 59 58 57 56 54 55 54 53 52 50 51 50 50* 49 48 47 46 (A) number 17.4 56.9 11.5 11.6 2.3 0.3 49.4 50.6 9.2 49.8 23.5 7.6 9.0 0.9 100 7.7 36.7 7.7 27.4 20.5 39.5 60.5 0.6 18.6 4.1 27.8 48.9 30.9 69.1 1.1 3.7 1.2 26.2 67.8 100 0.3 2.2 91.7 5.8 100 2.4 9.5 83.8 4.3 99.75 0.25 5.2 5.5 74.0 7.3 8.0 Percentage 85.91062 83.911504 82.91413 81.91348 79.91639 77.920368 80.91634 78.91835 81.9167 79.91651 77.91735 76.91993 75.91923 73.9224 74.92158 75.9214 73.9211 72.9234 71.92174 69.92428 70.92484 68.92568 69.92535 67.92486 66.92715 65.92605 63.929145 64.92779 62.92959 63.92796 61.92834 60.93105 59.93078 57.93534 58.933189 57.93327 56.93539 55.93493 53.93962 54.938054 53.938879 52.940651 51.940514 49.946051 50.943978 49.947165 49.944789 48.947867 47.947948 46.95176 45.952633 mass Atomic 193

Table of naturally RADIOACTIVITY occurring isotopes 3 Key words atomic mass atomic number Table of masses and abundance of naturally occurring isotopes isotope mass number Atomic Element Symbol Mass Percentage Atomic number number mass (Z) (A) Atomic number 37 Rubidium Rb 85 72.1 84.9117 ● The atomic number (Z) of an element 87* 27.9 86.9092 is the number of protons in the 38 Strontium Sr 84 0.6 83.91338 nucleus of one atom of that element. 86 9.9 85.9093 All atoms of the same element have 87 7.0 86.9089 the same atomic number. 88 82.5 87.9056 39 Yttrium Y 89* 100 88.9054 Element 40 Zirconium Zr 90 51.5 89.9043 ● “Element” refers to the common name 91 11.2 90.9052 of the element. This list is restricted to 92 17.1 91.9046 94 17.4 93.9061 the 89 naturally occurring elements. 96 2.8 95.9082 41 Niobium Nb 93 100 92.9060 Symbol 42 Molybdenum Mo 92 15.9 91.9063 ● “Symbol” refers to the shorthand form 94 9.1 93.9047 of the element’s name used in 95 15.7 94.9057 chemical equations. 96 16.5 95.9045 97 9.4 96.9057 Mass number 98 23.8 97.9055 ● The mass number (A) represents the 100 9.6 99.9076 number of protons or neutrons in the 43 Technetium Tc has no stable or naturally- occuring isotopes nucleus of one atom of that element. 44 Ruthenium Ru 96 5.6 95.9076 Not all atoms of the same element 98 1.9 97.905 have the same mass number. Atoms of 99 12.7 98.9061 an element that have different mass 100 12.6 numbers are called isotopes. 101 17.1 102 31.6 101.9037 Percentage 104 18.5 103.9055 ● “Percentage” refers to isotopic 45 Rhodium Rh 103 100 102.9048 abundance. For example, 99.99 46 Palladium Pd 102 1.0 101.9049 percent of naturally-occurring 104 11.0 103.9036 hydrogen has the mass number 1. 105 22.2 104.9046 Only 0.01 percent has the mass 106 27.3 105.9032 108 26.7 107.9039 number 2. 110 11.8 109.9045 47 Silver Ag 107 51.4 106.9050 Atomic mass 109 48.6 108.9047 ● “Atomic mass” refers to the average 48 Cadmium Cd 106 1.2 105.9059 atomic mass of that element's isotope 108 0.9 107.9040 weighted by isotopic abundance. 110 12.4 109.9030 111 12.7 110.9041 112 24.1 111.9028 113 12.3 112.9046 114 28.8 113.9036

116 7.6 115.9050 mation Ltd. 49 Indium In 113 4.3 112.9043 or 115* 95.7 114.9041 Visual Inf *denotes radioactive isotope © Diagram © Diagram Visual Information Ltd. ● Atomic mass ● Percentage ● Mass number ● Symbol ● Element ● Atomic number mass number isotope atomic number atomic mass Key words weighted byisotopicabundance. atomic massofthatelement'sisotope numbers arecalledisotopes an elementthathavedifferentmass Atomic mass “Atomic number 2. Only 0.01percenthasthemass hydrogen hasthemassnumber1. percent ofnaturally abundance. For example,99.99 “Percentage” referstoisotopic have thesamemassnumber Not allatomsofthesameelement nucleus ofoneatomthatelement. number ofprotonsorneutronsinthe The chemical equations. of form “Symbol” referstotheshorthand elements. the 89naturallyoccurring of theelement.Thislistisrestrictedto “Element” referstothecommonname the sameatomicnumber All atomsofthesameelementhave nucleus ofoneatomthatelement. is thenumberofprotonsin The the element’snameusedin mass number atomic number RADIOACTIVITY ” 194 refers totheaverage (A) representsthe -occurring (Z) ofanelement . . . Atoms of * occurring isotopes4 Table ofnaturally denotes radioactive isotope 59 58 57 56 55 54 53 52 51 50 Table of masses andabundance of naturally occurring isotopes (Z) number Atomic Praseodymium Cerium Lanthanum Barium Cesium Xenon Iodine Tellurium Antimony Tin lmn yblMass Symbol Element Pr Ce La Ba Ca Xe I Te Sb Sn 141 142* 140 138 136 139 138* 138 137 136 135 134 132 130 133 136 134 132 131 130 129 128 126 124 127 130 128 126 125 124 123 122 120 123 121 124 122 120 119 118 117 116 115 114 112 (A) number 100 11.1 88.5 0.2 0.2 99.9 0.1 70.4 11.9 8.1 6.7 2.6 0.2 0.1 100 8.9 10.4 26.9 21.2 4.1 26.4 1.9 0.1 0.1 100 34.5 31.8 18.7 7.0 4.6 0.9 2.4 0.1 42.7 57.3 6.0 4.7 33.0 8.8 24.0 7.6 14.2 0.3 0.6 1.0 Percentage 140.90739 141.9090 139.90528 137.9057 135.9071 138.9061 137.9068 137.9050 136.9056 135.9044 134.9056 133.9043 131.9051 129.90625 132.9051 135.90722 133.90540 131.90416 130.90509 129.90351 128.90478 127.90354 125.90417 123.9061 126.90435 129.9067 127.9047 125.90324 124.9044 123.9028 122.9042 121.9030 119.9045 122.9041 120.9037 123.9052 121.9034 119.9021 118.9034 117.9018 116.9031 115.9021 114.9035 113.9030 111.9049 mass Atomic 195

Table of naturally RADIOACTIVITY occurring isotopes 5 Key words atomic mass atomic number Table of masses and abundance of naturally occurring isotopes isotope mass number Atomic Element Symbol Mass Percentage Atomic number number mass (Z) (A) Atomic number 60 Neodymium Nd 142 27.3 141.90748 ● The atomic number (Z) of an element 143 12.3 142.90962 is the number of protons in the 144* 23.8 143.90990 nucleus of one atom of that element. 145 8.3 144.9122 All atoms of the same element have 146 17.1 145.9127 the same atomic number. 148 5.7 147.9165 150 5.5 149.9207 Element 61 Promethium Pm has no naturally occuring isotope ● “Element” refers to the common name 62 Samarium Sm 144 3.1 143.9116 147* 15.1 146.91462 of the element. This list is restricted to 148 11.3 146.9146 the 89 naturally occurring elements. 149 14.0 148.9169 150 7.5 149.9170 Symbol 152 26.6 151.9193 ● “Symbol” refers to the shorthand form 154 22.4 153.9217 of the element’s name used in 63 Europium Eu 151 47.8 150.9196 chemical equations. 153 52.2 152.9207 64 Gadolinium Gd 152 0.2 151.9194 Mass number 154 2.2 153.9202 ● The mass number (A) represents the 155 15.1 154.9220 number of protons or neutrons in the 156 20.6 155.9222 157 15.7 156.9240 nucleus of one atom of that element. 158 24.5 157.9242 Not all atoms of the same element 160 21.7 159.9273 have the same mass number. Atoms of 65 Terbium Tb 159 100 158.924 an element that have different mass 66 Dysprosium Dy 156 0.1 numbers are called isotopes. 158 0.1 160 2.3 159.924 Percentage 161 19.0 160.926 ● “Percentage” refers to isotopic 162 25.5 161.926 abundance. For example, 99.99 163 24.9 162.928 percent of naturally-occurring 164 28.1 163.928 hydrogen has the mass number 1. 67 Holmium Ho 165 100 164.930 68 Erbium Er 162 0.1 Only 0.01 percent has the mass 164 1.6 163.929 number 2. 166 33.4 165.929 167 22.9 166.931 Atomic mass 168 27.1 167.931 ● “Atomic mass” refers to the average 170 14.9 169.935 atomic mass of that element's isotope 69 Thulium Tm 169 100 weighted by isotopic abundance. 70 Ytterbium Yb 168 0.1 170 3.1 171 14.4 172 21.9 171.929 173 16.2

174 31.7 173.926 mation Ltd.

176 12.6 or 71 Lutetium Lu 175 97.4

176* 2.6 175.9414 Visual Inf

*denotes radioactive isotope © Diagram © Diagram Visual Information Ltd. ● Atomic mass ● Percentage ● Mass number ● Symbol ● Element ● Atomic number mass number isotope atomic number atomic mass Key words weighted byisotopicabundance. atomic massofthatelement'sisotope numbers arecalledisotopes an elementthathavedifferentmass Atomic mass “Atomic number 2. Only 0.01percenthasthemass hydrogen hasthemassnumber1. percent ofnaturally abundance. For example,99.99 “Percentage” referstoisotopic have thesamemassnumber Not allatomsofthesameelement nucleus ofoneatomthatelement. number ofprotonsorneutronsinthe The chemical equations. of form “Symbol” referstotheshorthand elements. the 89naturallyoccurring of theelement.Thislistisrestrictedto “Element” referstothecommonname the sameatomicnumber All atomsofthesameelementhave nucleus ofoneatomthatelement. is thenumberofprotonsin The the element’snameusedin mass number atomic number(Z)ofanelement RADIOACTIVITY ” 196 refers totheaverage (A) representsthe -occurring . . . Atoms of * occurring isotopes6 Table ofnaturally denotes radioactive isotope (Z) number Atomic 81 80 79 78 77 76 75 74 73 72 Table of masses andabundance of naturally occurring isotopes lmn yblMass Symbol Element Thallium Mercury Gold Platinum Iridium Osmium Rhenium Tungsten Tantalum Hafnium Tl Hg Au Pt Ir Os Re W Ta Hf 210* 208* 207* 206* 205 203 204 202 201 200 199 198 196 197 198 196 195 194 192 190 193 191 192* 190* 189 188 187 186 184 187* 185 186 184 183 182 180 181 180 180 179 178 177 176 174 (A) number — — — — 70.5 29.5 6.9 29.8 13.2 23.1 16.9 10.0 0.1 100 7.2 32.9 0.8 61.5 38.5 16.1 13.3 1.6 1.6 0.02 62.9 37.1 28.4 30.6 14.4 26.4 0.2 99.99 0.01 35.2 13.7 27.1 18.6 5.2 0.2 Percentage 209.99000 207.98201 206.97745 205.97608 204.97446 202.97233 203.97348 201.97063 200.97031 199.96834 198.96826 197.96677 195.96582 196.96655 197.9675 195.9646 194.9645 193.9624 191.9605 189.9592 192.9623 190.9599 191.9605 189.9574 188.9572 187.9550 186.9550 185.9529 186.9550 184.950 185.951 183.9491 182.9485 181.9465 179.9450 180.9462 179.9457 179.9451 178.9444 177.9425 176.9419 175.9403 mass Atomic 197

Table of naturally RADIOACTIVITY occurring isotopes 7 Key words atomic mass atomic number Table of masses and abundance of naturally occurring isotopes isotope mass number Atomic Element Symbol Mass Percentage Atomic number number mass (Z) (A) Atomic number 82 Lead Pb 204 1.4 203.97307 ● The atomic number (Z) of an element 206 25.2 205.97446 is the number of protons in the 207 21.7 206.97590 nucleus of one atom of that element. 208 51.7 207.97664 All atoms of the same element have 210* — 209.98418 the same atomic number. 211* — 210.98880 212* — 211.99190 Element 214* — 213.99976 ● “Element” refers to the common name 83 Bismuth Bi 209 100 208.98042 210* — 209.98411 of the element. This list is restricted to 211* — 210.98729 the 89 naturally occurring elements. 212* — 211.99127 214* — 213.99863 Symbol 84 Polonium Po 210* — 209.98287 ● “Symbol” refers to the shorthand form 211* — 210.98665 of the element’s name used in 212* — 211.98886 chemical equations. 214* — 213.99519 215* — 214.99947 Mass number 216* — 216.00192 ● The mass number (A) represents the 218* — 218.0089 number of protons or neutrons in the 85 Astatine At 215* — 214.99866 218* — 218.00855 nucleus of one atom of that element. 86 Emanation Em 219* — 219.00952 Not all atoms of the same element 220* — 220.01140 have the same mass number. Atoms of 222* — 222.0175 an element that have different mass 87 Francium Fr 223* — 223.01980 numbers are called isotopes. 88 Radium Ra 223* — 223.01857 224* — 224.02022 Percentage 226* — 226.0254 ● “Percentage” refers to isotopic 228* — 228.03123 abundance. For example, 99.99 89 Actinium Ac 227* — 227.02781 percent of naturally-occurring 228* — 228.03117 hydrogen has the mass number 1. 230* — 230.0331 Only 0.01 percent has the mass 231* — 231.03635 232* 100 232.03821 number 2. 234* — 234.0436 91 Protactinium Pa 231* — 231.03594 Atomic mass 234* — 234.0434 ● “Atomic mass” refers to the average 92 Uranium U 234* 0.006 234.04090 atomic mass of that element's isotope 235* 0.718 235.04393 weighted by isotopic abundance. 238* 99.276 238.0508

KEY WORDS

alkyne A member of the hydrocarbon group with the Key words general formula CnH2n–1. They have a triple bond between a pair of carbon atoms in each molecule and are thus reactive. accelerator A chemical that increases the rate of a chemical allotrope An element that can exist in more than one reaction. physical form while in the same state. acid Any substance that releases hydrogen ions when added alloy A metallic material made of two or more metals or of a to water. It has a pH of less than 7. metal and non-metal. acid-base indicator A chemical compound that changes alpha decay The process of radioactive decay in which the color when going from acidic to basic solutions. An example nucleus of an atom emits an alpha particle. is Methyl orange. alpha particle A particle released during radioactive decay acidity The level of hydrogen ion concentration in a that consists of two neutrons and two protons. solution. aluminum (Al) A silvery-white. metallic element that is actinides The name of the radioactive group of elements non-magnetic and oxidizes easily. with atomic numbers from 89 (actinium) to 103 amine A member of a group of organic compounds (lawrencium). containing the amino functional group –NH2. actinium (Ac) A silvery radioactive metallic element that amino acid An organic compound containing both the occurs naturally in pitchblende and can be synthesized by carboxyl group (–COOH) and the amino group (–NH2). bombarding radium with neutrons. ammonia (NH3) A colorless, strong-smelling poisonous gas actinium series One of the naturally occurring radioactive that is very soluble in water. series. ammonium hydroxide (NH4OH) An aqueous solution activation energy The energy barrier to be overcome in of ammonia. It is a corrosive chemical with a strong odor. order for a reaction to occur. ammonium ion (NH4+) An ion found in ammonia active site The part of an enzyme where the chemical solution and in ammonium compounds. reaction occurs. amphoteric Exhibiting properties of both an acid and a base. addition polymerization A chemical reaction in which anhydride The substance remaining when one or more simple molecules are added to each other to form long-chain molecules of water have been removed from an acid or a molecules without by-products. base. addition reaction A reaction in which a molecule of a anhydrous Containing no water.Term applied to salts substance reacts with another molecule to form a single without water of crystallization. compound. anion An ion having a negative charge. adsorption The process by which molecules of gases or anode The electrode carrying the positive charge in a liquids become attached to the surface of another substance. solution undergoing electrolysis. aerosol Extremely small liquid or solid particles suspended anomer A stereoisometric form of a sugar, involving in air or another gas. different arrangements of atoms or molecules around a alcohol A member of a family of organic compounds whose central atom, structure contains the –OH functional group. aqueous solution A solution in which water is the solvent. aldehyde One of a group of organic compounds containing argon Ar.A colorless, odorless. gaseous element. One of the the aldehyde group (–CHO). Names have the suffix -al. noble gases. aldohexose A monosaccharide having six carbon atoms and aryl A member of an aromatic hydrocarbon group formed by an aldehyde group. the removal of a hydrogen atom from an aromatic aldose A sugar containing one aldehyde group per molecule hydrocarbon. alkali A solution of a substance in water that has a pH of association The process by which molecules of a substance more than 7 and has an excess of hydroxide ions in the combine to form a larger structure. solution. astatine At. A non-metallic radioactive element that is highly alkali metals Metallic elements found in group 1 of the unstable and rare in nature. periodic table. They are very reactive, electropositive, and atmosphere The layer of gases surrounding Earth. react with water to form alkaline solutions. atom The smallest particle of an element that can exhibit alkaline earth metals Metallic elements found in group 2 that element’s properties. of the periodic table. atomic emission spectrum The amount of alkalinity Having a pH greater than 7. electromagnetic radiation an element emits when excited. alkane A member of the hydrocarbon group whose general atomic mass The ratio of the mass of an average atom of formula is CnH2n+2. They have single bonds between the an element to 1/12th of the mass of an atom of the carbon-12 carbon atoms and are not very reactive. isotope. mation Ltd. or alkanol See alcohol atomic number The number of protons in the nucleus of alkene A member of the hydrocarbon group whose general an atom.

Visual Inf formula is CnH2n. They have a double bond between a pair of atomic volume The volume of one mole of the atoms of carbon atoms and are thus reactive. an element. alkyl A member of the hydrocarbon group whose general Avogadro’s constant The number of particles present in

KEY WORDS azeotropic mixture A mixture of liquids that boils without cathode The electrode carrying the negative charge in a a change in composition. solution undergoing electrolysis. bakelite A phenol/methanal resin that has good electrical cathode rays A stream of electrons emitted from the and heat insulation properties. cathode in a vacuum tube. base A substance existing as molecules or ions that can take cation An ion having a positive charge. up hydrogen ions. cellulose A complex carbohydrate that is the main beta decay The process of radioactive decay in which the component of the cell walls of plants. nucleus of an atom emits a beta particle. centrifuge A machine that rotates an object at high speed. beta particle A high-speed electron emitted by the nucleus chain reaction A self-sustaining nuclear reaction yielding of certain radioactive elements during beta decay. energy and electrons emitted by the fission of an atomic Big Bang The primeval explosion that most astronomers nucleus, which proceeds to cause further fissions. think gave rise to the Universe. chemical compound A substance composed of two or black hole An object with infinite density. more elements linked by chemical bonds that may be ionic or body-centered cubic packing A crystalline structure in covalent. which one atom sits in the center of each cube. chemical energy The energy stored in the bonds between boiling point The point at which a substance changes from atoms and molecules that is released during a chemical the liquid state to the gas state. reaction. bond The chemical connection between atoms within a chemical reaction The process in which one or more molecule. Bonds are forces and are caused by electrons. substances reacts to form new substances. bond angle In a molecule, the angle between the two chiral An object or a system that differs from its mirror straight lines joining the centers of the atoms concerned. image. bromine (Br) A non-metallic element that is isolated as a chloride A compound containing chlorine and another dark red liquid. It is a very reactive oxidizing agent. element. brown dwarf A ball of gas like a star but whose mass is too chlorine (Cl) A poisonous, greenish, gaseous element that small to have nuclear fusion occur at its core. is a powerful oxidizing agent. Brownian motion The random movement of particles chlorophyll A green pigment found in most plants. It through a liquid or gas. absorbs light energy during photosynthesis. buckminsterfullerene See buckyball. chromatography A technique for separating and buckyball The nickname for buckminsterfullerene. An identifying mixtures of solutes in a solution. allotropic form of carbon. It has a cage-like structure and has chromium (Cr) A hard, brittle, gray-white metallic element the formula C50, C60, or C70. that is very resistant to corrosion and takes a high polish. burette A long, graduated glass tube with a tap at the lower cobalt (Co) A hard, lustrous, silvery-white metallic element end. It is used to measure a volume of liquid accurately. found in ores, calcium (Ca) A soft, slivery-white metal. colloid A substance made of very small particles whose size calcium carbonate A white solid, occurring naturally in (1–100 nm) is between those of a suspension and those in marble and limestone, that dissolves in dilute acids. solution. carbide A compound that contains carbon and an element compound See chemical compound with lower electronegativity. concentration A measure of the quantity of solute carbon (C) A non-metallic element whose compounds dissolved in a solution at a given temperature. occur widely in nature. conductor A material that is able to conduct heat and carbonate A salt of carbonic acid (containing the ion electricity. 2– CO3 ). convection current A circular current in a fluid such as air. carbon cycle The circulation of carbon through the coordinate bonding A type of covalent bond in which one biosphere. of the atoms supplies both electrons. carbon dioxide (CO2) A dense, colorless, odorless gas coordination number The number of atoms, ions, or that does not support combustion. It exists in the molecules to which bonds can be formed. atmosphere and is instrumental in the carbon cycle. copper (Cu) A pinkish metallic element used widely in carbonic acid (H2CO3) A very weak acid formed by alloys and electrical wires. dissolving carbon dioxide in water. covalent bond A bond formed when two electrons are carbon monoxide(CO) A colorless, odorless, very shared between two atoms (usually between two non-metallic poisonous gas. It is sparingly soluble in water. atoms), one contributed by each atom. carboxyl group The organic radical –CO.OH. covalent compound A compound in which the atoms in carboxylic acid An organic acid that contains one or more the molecules are held together by covalent bonds. carboxyl groups. crust The outer layer of Earth. mation Ltd. catalyst A substance that alters the rate of a chemical cryolite A compound of aluminum fluoride and sodium or reaction but remains chemically unchanged by it. fluoride.

catalytic cracking The process used in the petroleum crystal A substance with an orderly arrangement of atoms, Visual Inf industry to convert large-chain hydrocarbon molecules to ions, or molecules in a regular geometrical shape. smaller ones. daughter nucleus In radio active decay, the nucleus catenation The formation of chains of bonded atoms. produced by the decay of the previous nucleus. © Diagram 200

KEY WORDS

dehydrating agent A substance that has an attraction for equivalence point The point at which there are equivalent water and is therefore used as a drying agent. amounts of acid and alkali. dehydrogenation The chemical process of removal of ester A member of a hydrocarbon group that is formed by a hydrogen atoms from a molecule (a form of oxidation), reaction between a carboxylic acid and an alcohol. increasing its degree of unsaturation. ethane (C2H6) A colorless, flammable alkane that occurs in density The mass per unit volume of a given substance. natural gas. detergent The term for a synthetic soap substitute. ethanol (C2H5OH) A volatile, colorless liquid alcohol used diamond A transparent crystalline allotrope of carbon. It is in beverages and as a gasoline octane enhancer. the hardest naturally occurring substance. ethene (C2H4) A colorless, flammable unsaturated gas, diatomic molecule A molecule that consists of two atoms. manufactured by cracking petroleum gas, used in ethanol and diffusion The process of rapid random movement of the polyethene production. particles of a liquid or gas that eventually form a uniform evaporation The change in state from liquid to vapor. mixture. exothermic A chemical change resulting in the liberation of dipole A chemical compound with an unequally distributed heat. electric charge. face-centered cubic close packing A crystal structure disaccharide A sugar molecule formed by a condensation in which one atom sits in each “face” of the cube. reaction between two monosaccharide molecules. Faraday constant The amount of electricity needed to displacement reaction A reaction in which a more liberate one mole of a monovalent ion during electrolysis reactive substance displaces the ions of a less reactive (9.648 670 x 10–4 C mol–1). substance. fatty acid A hydrocarbon chain with a carboxyl group at dissociation The breaking down of a molecule into smaller one end. molecules, atoms, or ions. filtrate A clear liquid that has passed through a filter. dissolve To add a solute to a solvent to form a uniform filtration The process of removing particulate matter from solution. a liquid by passing the liquid through a porous distillation A process in which a solution is boiled and its substance. vapor then condensed. fission A process during which a heavy atomic nucleus double bond A covalent bond formed between two atoms disintegrates into two lighter atoms and the lost mass is in which two pairs of electrons contribute to the bond.. converted to energy. dry gas A gas from which all water has been removed fluorescence The emission of light from an object that has ductile Capable of being drawn out, shaped, or bent. been irradiated by light or other radiations. effective collision A collision that brings about a reaction. fluorine (F) A gaseous non-metallic element that is electric field A field of force around a charged particle. poisonous and very reactive gas. electrode A conductor that allows current to flow through flux A substance that combines with another substance an electrolyte, gas, vacuum, or semiconductor. (usually an oxide), forming a compound with a lower melting electrolysis The process by which an electrolyte is point than the oxide. decomposed when a direct current is passed through it foam A dispersion of gas in a liquid or solid. Small bubbles between electrodes. of gas are separated by thin films of the liquid or solid. electrolyte A substance that forms ions when molten or formula mass The relative molecular mass of a compound dissolved in a solvent and that carries an electric current calculated using its molecular formula. The mass of a mole of during electrolysis. the substance. electron One of the three basic subatomic particles. Very forward reaction A reaction in which reactants are light and carrying a negative charge, it orbits around the converted to products. nucleus of an atom. fractional distillation The separation of a mixture or element A substance that cannot be split into simpler liquids that have differing but similar boiling points. substances using chemical methods. fullerenes Allotropes of carbon in the form of a hollow emulsion A colloidal dispersion of small droplets of one sphere (buckyball) or tube (nanotube). liquid dispersed within another, such as oil in water or water functional group The atom (or group of atoms) present in in oil. a molecule that determines the characteristic properties of enantiomer One of two “mirror images” of a chiral that molecule. molecule. fusion The process by which two or more light atomic end point The point at which a reaction is complete. nuclei join, forming a single heavier nucleus. The products of endothermic a chemical change during which heat is fusion are lighter than the components. The mass lost is absorbed. liberated as energy. enthalpy A measure of the stored heat energy of a galvanizing The coating of iron or steel plates with a layer mation Ltd. or substance. of zinc to protect against rusting. enzyme An organic catalyst, made of proteins, that increases gamma radiation Very short-wave electromagnetic

Visual Inf the rate of a specific biochemical reaction. radiation emitted as a result of radioactive decay. equilibrium The state of a reversible chemical reaction gas One of the states of matter. In a gas, the particles can where the forward and backward reactions take place at the move freely throughout the space in which it is contained.

KEY WORDS gas-liquid chromatography A type of chromatography helium (He) A colorless, odorless gaseous element that is in which the mobile phase is a carrier gas and the stationary the second most abundant element on Earth. phase is a microscopic layer of liquid on an inert solid hexagonal close packing In crystalline structures, a way support. of packing atoms so that alternating layers overlie one gel A colloidal solution that has formed a jelly. The solid another in an ABABAB pattern. particles are arranged as a fine network in the liquid phase. hexose A monosaccharide with six carbon atoms. geometric isomerism A form of isomerism that describes homologous series A series of related organic the orientation of functional groups at the ends of a bond compounds. The formula of each member differs from the where no rotation is possible. preceding member by the addition of a –CH2– group. glucose In animals and plants, the most widely distributed hydration The combination of water and another substance hexose sugar and the most common energy source in to produce a single product. respiration. hydride A compound formed between hydrogen and glycogen A polysaccharide composed of branched chains of another element. glucose, used to store energy in animals and some fungi.. hydrocarbon An organic molecule consisting only of gold (Au) A shiny, yellow metallic element used in coins, carbon and hydrogen. jewelry, and electrical contacts. hydrochloric acid (HCl) A colorless fuming solution of grade The concentration of ore in rock. hydrogen chloride. Graham’s law The velocity with which a gas will diffuse is hydrogen (H) An odorless, easily flammable gaseous inversely proportional to the square root of its density. element that is the most abundant on Earth. graphite A soft, grayish-black, solid allotrope of carbon. hydrogen bond A weak bond between hydrogen and ground state The lowest allowed energy state of an atom, another element with partial but opposite electrical charges. molecule, or ion. hydrogen chloride (HCl) A colorless gas with a pungent group The vertical columns of elements in the periodic smell that fumes in moist air. It is very soluble in water. table. Elements in a group react in a similar way and have hydrogen peroxide (H2O2) A colorless or pale blue similar physical properties. viscous liquid. It is a strong oxidizing agent, but it can also act group 1 elements The alkali metals. The elements lithium, as a reducing agent. sodium, potassium, rubidium, cesium, and francium. These hydrogen sulfide (H2S) A colorless, poisonous gas elements have one electron in their outer shell. smelling of bad eggs that is moderately soluble in water. It is group 2 elements The alkaline earth metals. The a reducing agent. + elements beryllium, magnesium, calcium, strontium, barium, hydronium ion The positive ion (H3O) . It is the hydrated and radium. These elements have two electrons in their outer form of the hydrogen ion (H+) or proton. shell. hydrophilic Water-loving. In solution, it refers to a chemical group 3 elements The elements boron, aluminum, or part of a chemical that is highly attracted to water. gallium, indium, and thallium. These elements have a full s hydrophobic Water-hating. It refers to a chemical or part of orbital and one electron in a p orbital in their outer shell. a chemical that repels water. group 4 elements The elements carbon, silicon, hydroxide A compound containing the hydroxide ion or the germanium, tin, and lead. These elements have a full s orbital hydroxyl group bonded to a metal atom. and two electrons in two p orbitals in their outer shell. hydroxide ion The negative ion (OH–) present in alkalis. group 5 elements The elements nitrogen, phosphorus, immiscible Incapable of mixing. arsenic, antimony, and bismuth. These elements have a full s indicator A substance that indicates by a change in its color orbital and three electrons in three p orbitals in their outer the degree of acidity or alkalinity of a solution or the shell. presence of a given substance. group 6 elements The chalcogens. The elements oxygen, inert A substance that is either very or completely sulfur, selenium, tellurium, and polonium. These elements unreactive. have a full s orbital, one full p orbital, and two half-full p inert gases See noble gases. orbitals in their outer shell. infrared Electromagnetic radiation with a greater group 7 elements The halogens. The elements fluorine, wavelength than the red end of the visible spectrum. chlorine, bromine, iodine, and astatine. These elements have insoluble A substance that does not dissolve in a particular a full s orbital, two full p orbitals, and one half-full p orbital in solvent under certain conditions of temperature and their outer shell. pressure. group 8 elements. The noble or inert gases. The elements iodine (I) A grayish-black non-metallic element that is helium, neon, argon, krypton, xenon, and radon. The outer essential in the diet and is used in disinfectants and shell of the atoms in these elements is complete, rendering photography. these elements unreactive. ion An electrically charged atom or group of atoms. mation Ltd. half-life The time required for half the atoms of a ionic bonding A type of bonding that occurs when atoms or radioactive substance to disintegrate. form ions and electrons are transferred from one atom to halide A compound that a halogen makes with another another. Visual Inf element. Metal halides are ionic; non-metal halides are ionic compound Compounds consisting of ions held formed by covalent bonding. together by strong ionic bonds. Ionic compounds are halogens See Group 7 elements. electrolytes. © Diagram 202

KEY WORDS

ionic crystal A type of crystal where ions of two of more mass spectrometry A technique for determining the elements form a regular three-dimensional arrangement composition of molecules by using the mass of their basic (crystal structure). constituents ionization energy The energy needed to remove melting point The point at which a substance changes completely an electron from a neutral gaseous atom or ion state from solid to liquid. against the attraction of the nucleus. methane (CH4) The simplest alkane. A colorless, tasteless, ionizing radiation Any radiation capable of displacing odorless flammable gas used as a fuel. electrons from atoms or molecules and so producing ions mineral A natural inorganic substance with distinct chemical iron (Fe) A silvery, malleable and ductile metallic element composition and internal structure. used in construction. mixture A system consisting of two or more substances that irradiation The use of radiation to destroy microorganisms are not chemically combined. in foods. mobile phase The phase that moves along the stationary isomer One of two or more (usually organic) compounds phase. It is the solvent in paper chromatography. having the same molecular formula and relative molecular molarity The concentration of solution giving the number mass but different three-dimensional structures. of moles of solute dissolved in 1 kg of solvent. isomerism The rearrangement atoms in a molecule to mole The amount of a substance that contains the same make it more efficient. number of entities (atoms, molecules, ions, etc.) as there are isomerization The transformation of a molecule into a atoms in 12 g of the carbon-12 isotope. different isomer. molecular mass The sum of the atomic masses of all isotope Atoms of the same element (all chemically identical) atoms in a molecule. The mass of a mole of the substance. having the same atomic number but containing different molecule The smallest part of an element or chemical numbers of neutrons, giving a different mass number. compound that can exist independently with all the ketone An organic compound that contain two organic properties of the element or compound. radicals connected to a carbonyl group. monomer A basic unit from which a polymer is made. kinetic energy The energy a body has by virtue of its monosaccharide A simple sugar such as glucose. motion. nanotube An isotope of carbon consisting of long thin lanthanide series A series of metallic elements with the cylinders closed at either end with caps containing atomic numbers 57 to 71. The metals are shiny and are pentagonal rings. attacked by water and acids. neptunium (Np) A radioactive metallic element that can be lattice The orderly three-dimensional arrangements of synthesized by bombarding U-238 with neutrons. atoms, molecules, or ions seen in crystals. neptunium series A radioactive series composed of lead (Pb) A silvery-white metallic element used in batteries artificial isotopes. and in water, noise, and radiation shielding. neutral A solution whose pH is 7. lead sulfide (PbS) A brownish-black insoluble crystal. It neutralization The reaction of an acid and a base forming a occurs naturally as the mineral galena. salt and water.. Le Chatelier’s principle If a chemical reaction is at neutron One of the two major components of the atomic equilibrium and a change is made to any of the conditions, nucleus. It has no electric charge. further reaction will take place to counteract the changes in neutron star The smallest but densest kind of star, order to re-establish equilibrium. apparently resulting from a supernova explosion. limewater A solution of calcium hydroxide that is used to nickel (Ni) A hard, malleable and ductile, silvery-white test for the presence of carbon dioxide. metallic element that is a component of Earth’s core. limiting form The possibilities for the distribution of nitrate A salt of nitric acid. electrons in a molecule or ion. nitric acid (HNO3) A colorless, corrosive, poisonous, liquid A state of matter between solid and gas. Particles are fuming liquid that is a strong oxidizing agent. loosely bonded, so can move relatively freely. nitrite A salt of nitrous acid. lone pair A pair of electrons in the outermost shell of an nitrogen (N) A colorless gaseous element essential for the atom that are not involved in the formation of covalent growth of plants and animals. bonds. nitrogen cycle The process by which nitrogen is recycled luminescence Light emission from a substance caused by in the ecosystem. an effect other than heat. noble gases Group 8 elements: helium, neon, argon, magnesium (Mg) A silvery-white metallic element used in krypton, xenon, and radon. These gases do not combine alloys and castings. chemically with other materials. magnesium oxide (MgO) A white solid used for nucleon A proton or neutron. reflective coatings and as a component of semiconductors. nucleus The positively charged core of an atom that mation Ltd. or manganese (Mn) A soft, gray metallic element used in contains almost all its mass. making steel alloys. nuclide A particular isotope of an element, identified by the

Visual Inf mantle The layer of Earth between the crust and the core. number of protons and neutrons in the nucleus. mass The measure of a body’s resistance to acceleration. optical isomerism A form of isomerism in which two mass number The total number of protons and neutrons isomers are the same in every way except that they are mirror

KEY WORDS orbital An area around an atom or molecule where there is a protostar The early stage in a star’s formation before the high probability of finding an electron. onset of nuclear burning. ore A mineral from which a metal or non-metal may be quantum number The number used when describing the profitably extracted. energy levels available to atoms and molecules. oxidation The process by which a substance gains oxygen, racemate A mixture of equal amounts of left- and right- loses hydrogen, or loses electrons. handed stereoisomers of a chiral molecule. oxidation state The sum of negative and positive charges radiation Energy that is transmitted in the form of particles, in an atom. rays, or waves. oxide A compound consisting only of oxygen and another radical A group of atoms forming part of many molecules. element. Oxides can be either ionic or covalent. radioactive decay The process by which unstable oxidizing agent A substance that can cause the oxidation radioactive atoms are transformed into stable, non-radioactive of another substance by being reduced itself. atoms. oxygen (O) A colorless, odorless gaseous element. It the radioactivity The spontaneous disintegration of certain most common element in Earth’s crust and is the basis for isotopes accompanied by the emission of radiation. respiration in plants and animals.. rate of reaction The speed at which a chemical reaction ozone (O3) One of the two allotropes of oxygen. A bluish proceeds. gas with a penetrating smell, it is a strong oxidizing agent. reactant A substance present at the start of a chemical period The horizontal rows of elements in the periodic reaction that takes part in the reaction. table. reaction A process in which substances react to form new periodic table A table of elements, arranged in ascending substances. order of atomic number, that summarizes the major reactivity The ability of substances to react to form new properties of the elements. substances. periodicity Recurring at regular intervals. reactivity series of metals Metallic elements arranged 2– peroxide A compound that contains the peroxide ion O2 . in order of their decreasing chemical reactivity. Peroxides are strong oxidizing agents. reagent A substance that takes part in a chemical reaction, pH A scale from 0 to 14 that measures the acidity or alkalinity one that is usually used to bring about a chemical change. of a solution. A neutral solution has a pH of 7, while an acidic red giant A very large, cool star in the final stages of its life. solution has a lower value and an alkaline solution a higher redox reaction A process in which one substance is value. reduced and another is oxidized at the same time. pH meter A device that uses an electrochemical cell to reducing agent A chemical that can reduce another while measure pH. being oxidized itself. phosphorescence The emission of light by an object, and reduction A chemical reaction in which a substance gains the persistence of this emission over long periods, following electrons, looses oxygen, or gains hydrogen. It is the reverse irradiation by light or other forms of radiation. of oxidation. photochemical reaction A chemical reaction that is reforming The conversion of straight chain molecules into initiated by a particular wavelength of light. those that are branched in order to improve their efficiencies. photoelectric effect The emission of electrons from residfining The process used on the residue fraction of metals upon the absorption of electromagnetic radiation. crude oil to convert it into a usable product. photosynthesis The photochemical reaction by which residue The solid remaining after the completion of a green plants make carbohydrates using carbon dioxide and chemical process. water. resonance structure In organic chemistry, a diagrammatic platinum (Pt) A soft, shiny, silver metallic transition tool to symbolize bonds between atoms in molecules. element that is malleable and ductile. respiration The chemical reaction by which an organism pollutant A substance that harms the environment when it derives energy from food. mixes with air, soil, or water. reverse reaction A reaction in which the products are polyethene A thermoplastic polymer made by addition converted into reactants. polymerization of ethene. reversible reaction A chemical reaction that can proceed polymer A material containing very large molecules built up in either direction. It does not reach completion but achieves from a series of repeated small basic units (monomers). dynamic equilibrium. polymerization The building up of long chain Rf value The ratio of the distance moved by a substance in a hydrocarbons from smaller ones. chromatographic separation to the distance moved by the polysaccharide A organic polymer composed of many solvent. simple sugars (monosaccharides). rust A reddish-brown oxide coating on iron or steel caused precipitate An insoluble substance formed by a chemical by the action of oxygen and water. mation Ltd. reaction. salt A compound formed from an acid in which all or part of or product A substance produced during a chemical reaction. the hydrogen atoms are replaced by a metal or metal-like protein A large, complex molecule composed of a long group. Salts are generally crystalline. Visual Inf chain of amino acids. saponification The treatment of an ester (hydrolysis) with proton The positively charged particle found in the nucleus a strong alkaline solution to form a salt of a carboxylic acid of the atom. and an alcohol. © Diagram 204

KEY WORDS

saturated A solution where there is an equilibrium between sulfide A compound of sulfur and a more electropositive the solution and its solute. element. scandium (Sc) Silvery-white metallic element in the sulfur (S) A yellow, non-metallic element that is found lanthanide series found in nature only in minute quantities. abundantly in nature. sewage Wastewater from domestic and industrial sources. sulfuric acid (H2SO4) An oily, colorless, odorless liquid shell A group of orbitals at a similar distance from an atomic that is extremely corrosive. nucleus. sulfur dioxide (SO2) A colorless gas with a pungent odor silver (Ag) A white, shiny, ductile metallic element. of burning sulfur. It is very soluble in water. silver nitrate (AgNO3) A very soluble white salt that sulfur trioxide (SO3) A white, soluble solid that fumes in decomposes to form silver, oxygen, and nitrogen dioxide on moist air. It reacts violently with water to form sulfuric acid. heating. supernova The explosion caused when a massive star dies slag Waste material that collects on the surface of a molten and collapses. metal during the process of either extraction or refining. surface area The sum of the area of the faces of a solid. smelting The process of extracting a metal from its ores. suspension A type of dispersion. Small solid particles are soap A cleansing agent made from fatty acids derived from dispersed in a liquid or gas. natural oils and fats. tensile strength The amount of stress a material can stand sodium (Na) A soft, silver-white metallic element. without breaking. sodium chloride (NaCl) A nonvolatile ionic compound thorium Th. A gray, radioactive metallic element used as fuel that is soluble in water. in nuclear reactors. sodium hydroxide (NaOH) A white, translucent, thorium series One of the naturally occurring radioactive crystalline solid that forms a strongly alkaline solution in series. water. titanium (Ti) A lightweight, gray metallic element that is sol A liquid solution or suspension of a colloid. very strong and resistant to corrosion. solid A state of matter in which the particles are not free titration In analytical chemistry, A technique used to to move but in which they can vibrate about fixed determine the concentration of a solute in a solution. positions. transition metals Metallic elements that have an solubility A measure of the quantity of a solute that will incomplete inner electron structure and exhibit variable dissolve in a certain amount of solvent to form a saturated valencies. solution under certain conditions of temperature and triple bond A covalent bond formed between two atoms in pressure. which three pairs of electrons contribute to the bond. solubility curve A graphic representation of the changing ultraviolet Electromagnetic radiation of shorter solubility of a solute in a solvent at different temperatures. wavelengths than visible light, but of longer wavelength than soluble A relative term that describes a substance that can X rays. dissolve in a particular solvent. unit cell The smallest repeating array of atoms, ions, or solute A substance that dissolves in a solvent and thus forms molecules in a crystal. a solution. universal indicator A mixture of substances that shows a solution A uniform mixture of one or more solutes in a gradual color change over a wide range of pH values. solvent. uranium (U) A hard, white, radioactive metallic element solvent A substance, usually a liquid, in which a solute used in nuclear reactors and nuclear weapons. dissolves to form a solution. uranium series One of the naturally occurring radioactive species The common name for entities (atoms, molecules, series. molecular fragments, and ions) being subjected to valency The measure of an element’s ability to combine investigation. with other elements. spectrum The arrangement of electromagnetic radiation vanadium (V) A silvery-white or gray metallic element used into its constituent wavelengths. as a steel additive and in catalysts. starch A polysaccharide with the formula (C6H10O5). It is van der Waals forces Weak intermolecular or interatomic composed of many molecules of glucose. forces between neutral molecules or atoms. They are much stationary phase That which the mobile phase moves on. weaker than chemical bonds. In paper chromatography it is the paper. viscosity A measure of the resistance of a fluid to flow. stoichiometry The calculation of the quantities of reactants wavelength The distance between two corresponding and products involved in a chemical reaction. points on a wave. subatomic particles The particles from which atoms are white dwarf The small, dense remnant of a star near the made. Neutrons and protons are found in the nucleus of the end of its period of nuclear fusion. atom. Electrons form a cloud around the nucleus. zinc (Zn) A hard, brittle, bluish-white metallic element used mation Ltd. or sucrose A disaccharide sugar that occurs naturally in most in alloys and in galvanizing. plants. zwitterion An ion that carries both a positive and negative

INTERNET RESOURCES Chemistry Tutor Internet resources Help for high school students with chemistry homework. Includes an introduction to chemistry, equations, There is a lot of useful information on the internet. calculations, types of reactions, information on lab safety, Information on a particular topic may be available and links to other sources. through a search engine such as Google http://library.thinkquest.org/2923 (http://www.google.com). Some of the Web sites that are ChemSpy.com found in this way may be very useful, others not. Below is a selection of Web sites related to the material Links to chemistry and chemical engineering terms, covered by this book. definitions, synonyms, acronyms, and abbreviations. http://www.chemspy.com

The publisher takes no responsibility for the Chemtutor information contained within these Web sites. A guide to the basics of chemistry for high school and All the sites were accessible on March 1, 2006. college students. http://www.chemtutor.com About Chemistry Includes links to a glossary, encyclopedia, experiments, CHEMystery periodic table, chemical structure archive, chemistry A virtual chemistry textbook, providing an interactive problems, and articles. guide for high school chemistry students and links to http://chemistry.about.com other resources. http://library.thinkquest.org/3659 Allchemicals.info Hundreds of definitions and descriptions from absolute Common Molecules zero to zinc. Information and 3-D presentation on molecules studied http://www.allchemicals.info in chemistry classes or of interest for their structural properties. Chem4Kids http://www.reciprocalnet.org/edumodules/ Accessible information on matter, atoms, elements, commonmolecules reactions, biochemistry, and much more, for grades 5–9. Delights of Chemistry http://www.chem4kids.com Presents more than 40 chemistry demonstrations and 500 photographs/animations of experiments and Chemistry Carousel: A Trip Around the Carbon chemical reactions. Cycle http://www.chem.leeds.ac.uk/delights Site explaining the carbon cycle. http://library.thinkquest.org/11226 EnvironmentalChemistry.com Includes a chemical and environmental dictionary; a Chemistry Central detailed periodic table of elements; articles on Offers basic atomic information, information on the environmental and hazardous materials issues; a geologic periodic table, chemical bonding, and organic chemistry timeline. as well as extensive links to a wide variety of other http://environmentalchemistry.com resources. http://users.senet.com.au/~rowanb/chem Eric Weisstein’s World of CHEMISTRY Online encyclopedia, still under construction, with Chemistry.org excellent graphics; good source for chemical reactions. Offers publications, career advice, information, and http://scienceworld.wolfram.com/chemistry curriculum materials for K–12. General Chemistry Online

http://www.acs.org/ mation Ltd. Contains searchable glossary, frequently asked or The Chemistry Research Center questions, database of compounds, tutorials, Offers high school students links to useful sites for help simulations, and toolbox of periodic table and Visual Inf with homework. calculators.

INTERNET RESOURCES IUPAC Nomenclature Home Page Reactive Reports Definitions of terms used in chemistry provided by the Web chemistry magazine offering news stories and links International Union of Pure and Applied Chemistry. The to sites. “Gold book” is particularly good for basic terms. http://www.reactivereports.com http://www.chem.qmul.ac.uk/iupac ScienceMaster The Learning Matters of Chemistry News, information, links, columns, and homework help Offers visualizations of molecules and atomic orbits, in all major areas of science. interactive chemistry exercises, and links to other http://www.sciencemaster.com resources. http://www.knowledgebydesign.com/tlmc Science News for Kids Science Service Suggestions for hands-on activities, The Macrogalleria: A Cyberwonderland of books, articles, Web resources, and Polymer Fun other useful materials for students ages 9–13. An Internet “mall” for learning about polymers and http://www.sciencenewsforkids.org polymer science. http://www.pslc.ws/macrog The Science of Spectroscopy Nuclear Chemistry and the Community Introduction to spectroscopy with descriptions of common spectroscopic analysis techniques, as well as Introduction to nuclear chemistry and its impact on applications of spectroscopy in consumer products, society. medicine, and space science. http://www.chemcases.com/nuclear http://www.scienceofspectroscopy.info Open Directory Project: Biochemistry and Virtual Chemistry Molecular Biology 3-D simulated laboratory for teaching chemistry, with A comprehensive listing of internet resources in the links to an online encyclopedia, tutorials, and close-ups field of biochemistry. http://dmoz.org/Science/Biology/Biochemistry_and_ of molecules. http://neon.chem.ox.ac.uk/vrchemistry Molecular_Biology

Open Directory Project: Chemistry A Visual Interpretation of the Table of Elements A comprehensive listing of internet resources in the Striking visual representations of 110 elements. Site field of chemistry. includes detailed information on the elements and on http://dmoz.org/science/chemistry the history of the periodic table. http://www.chemsoc.org/viselements The pH Factor Introduction to acids and bases for middle school Web Elements™ Periodic Table Scholar Edition students. High quality source of information about the periodic http://www.miamisci.org/ph table for students. There is also a professional edition. http://www.webelements.com/webelements/scholar PSIgate: Chemistry Offers interactive tutorials, timeline, and links, in many What’s that Stuff? areas. Explores the chemistry of everyday objects. http://www.psigate.ac.uk/newsite/chemistry-gateway http://pubs.acs.org/cen/whatstuff/stuff.html mation Ltd. or Visual Inf © Diagram 207

INDEX catalysts 141–2 endothermic reactions 139 Index cathode ray oscilloscopes 17 energy levels 23 changes in matter 45–63 esters 165 chemical combination 41–4 ethene 158 Index of subject headings. chemical reactions 119–47 exothermic reactions 139 chlorine, compounds of 93 a chromatography 49–50 f collision theory 131 acids colloids 46 fertilizers, nitrate 79 neutralization of 130 compounds, molecular, masses of first ionization energy 27–8 preparation of 124 37 fission, nuclear 184 reactions of 123, 170 contact process 85–6 flame tests on metals 115 titration of 53–4 coordinate bonding 44 fractional distillation 47 actinium series 187 copper of crude oil 152 air, gases in 69 reactions of 111–12 fullerenes 149 alcohols 163, 170 smelting and conversion of 110 functional groups 162 alkalis, neutralization of 127 copper sulfate, solubility of 63 alkanes 156 covalent bonding 43 g reaction summary 169 crude oil, fractional distillation of alkenes 157 152 gas-liquid chromatography 50 reaction summary 169 crystal structure of metals 39–40 gases in air 69 allotropes crystals, ionic 38 Geiger and Marsden’s apparatus of carbon 148–9 14 of oxygen 82 d graphite 148 of sulfur 82 aluminum 106 decay sequences h reactions of 112 actinium series 187 amino acids 172 neptunium series 189 Haber process 74–5 ammonia 67, 73–7 radioactivity of 190 half-life 180–1 Haber process 74–5 thorium series 188 halogens 91–2, 95–7 properties of 73 uranium series 186 homologous series 162 atomic emission spectrum 22 detergents 166 hydrocarbons, naming of 155 atomic mass 35 diamonds 148 hydrogen 22–3, 64–8 atomic structure 13 disaccharides 174 hydrogen chloride 94 atomic volumes 33–4 distillation, simple and fractional Avogadro’s constant 20 47 i

b e ionic bonding 41 ionic crystals, structure of 38 bases 125–6 efficient packing 40 ionic radicals 42 neutralization of 128 electrode activity and ionic salts 59 boiling points 31–2 concentration 122 ionic solutions 60 bond dissociation energies 140 electrolysis 121–2 ionization energies of transition bonding of chemicals 41–4 electron structure of metals 104 metals 105 electrons 15–18 ionizing radiation 175 c elements iron atomic volumes of 33 smelting of 107 mation Ltd. carbon, chemistry of 148–74 boiling points of 31 reactions of 112 or carbon chains 154 first ionization energies of 27 isotopes carbon cycle 150 melting points of 29 naturally occurring 191–7 Visual Inf carbon oxides 151 organization of 25 radioactive 182

INDEX

l o s

lattice structure of metals 39 optical isomerism 171 salts luminescence 24 ores of metals 99, 113 formation of 126 organic compounds 167 ionic 59 m oscilloscopes 17 separation of solutions 48 oxidation and oxidation states sewage 57 mass 88, 143, 147 simple distillation 47 atomic 35 oxides of sulfur 84 smelting molecular 37 oxygen 80–3, 88–9 of copper 110 mass spectrometry 50 of iron 107 melting points 29–30 soaps 166 metal hydroxides 116 sodium 101 p metal ions 117 soil 55 metallic carbonates 129 paper chromatography 49 solar system 10 metals periodic table 26, 36 solubility, solutions and solvents crystal structure of 39–40 pH scale 51, 55 45, 48, 59, 61–3 electron structure of 104 planets stars 8–9 extraction of 113 composition of 11 steel manufacture 108 group 1 and group 2 100–3 density, size, and atmosphere of sulfur 80–3, 88, 90 ores of 99 12 oxides of 84 reactivity of 114, 119–20 polymers 159–61 sulfuric acid 85–7 tests on 115–17 polysaccharides 174 uses of 118 proteins 172 world distribution of 98 proton transfer 127–30 mixtures 45 t molecular mass 37 temperature, effect on reaction mole, the 21 rates of 137–8 molecules, size and motion of 19 r thorium series 188 monosaccharides 173 titration of acids 53–4 radiations transition metals 104–5 detection of 176 n as catalysts 142 properties of 177–8 naturally occurring isotopes radioactivity 175–97 191–7 of decay sequences 190 neptunium series 189 reaction rates 132–8 u neutralization of alkalis, bases and reactivity of metals 119–20 acids 127–30 redox reactions 144–6 uranium series 186 nitrate fertilizers 79 of halogens 96 nitric acid 76–7 reduction of oxygen and sulfur nitrogen 70–1, 77–8 88 w nitrogen cycle 72 refining processes 152–3 nuclear power 183–5 rusting 109 water 56–9, 67, 87 mation Ltd. or Visual Inf © Diagram