UNIT 1 SUMMARY MATTER – Anything that has mass and takes up space Other examples? PARTICLE – a single atom or groups of atoms that are bonded together and function as one unit Matter is found in phases or states: GAS • Indefinite shape and volume • Straight-line motion LIQUID • Indefinite shape, definite volume • Rolling motion SOLID • Definite shape and volume • Vibrating motion TYPES OF MATTER PURE SUBSTANCE – Matter where all the particles are identical He NaCl C12H22O11 There are two types of pure substances: ELEMENT • Made from only one type of atom • Cannot be broken into simpler substances by chemical means • Found on the Periodic Table Other examples? Gold Sulfur Helium Sodium COMPOUND • Made from two or more atoms joined together by chemical bonds • Can be broken down into simpler substances by chemical means (by breaking chemical bonds) Water Salt Sugar Other examples? Water Compound ↓ electricity Hydrogen and Oxygen ↓ electricity ↓ electricity Hydrogen and Oxygen Elements Salt Compound ↓ electricity Sodium and Chlorine ↓ electricity ↓ electricity Sodium and Chlorine Elements In CHEMICAL SEPARATION METHODS (e.g. electrolysis), chemical bonds are broken and/or formed. MIXTURE – Matter with different types of particles (elements and/or compounds) There are two types of mixtures: HETEROGENEOUS – Has distinct parts with different properties HOMOGENEOUS – Has same properties throughout (uniform composition) Air Jell-O Steel Brass SOLUTION – A homogenous mixture CLASSIFICATION OF MATTER CHANGES IN MATTER PHYSICAL CHANGE – One that does not change the identity of the matter Tearing Crushing Freezing Melting Boiling CHEMICAL CHANGE – One that does change the identity of matter through a CHEMICAL REACTION Burning Rusting Tarnishing Spoiling Exploding EVIDENCE OF A CHEMICAL CHANGE • Color change • A solid forms • Bubbles are formed • A flame is produced • Heat is absorbed or released Are these physical or chemical changes? • Cookies are baked • Water boils • Soap dissolves in water • A firefly emits light • Milk spoils • A metal chair rusts More examples of physical and chemical changes? CHEMICAL REACTION • Starting substance(s) called REACTANTS change into ending substances called PRODUCTS • Chemical bonds are broken and/or formed during the process Compound Element Compound Sugar Carbon + Water Reactant Products CONSERVATION OF MASS – Mass is neither created nor destroyed Reactants Product Iron + Oxygen Rust Fe + O2 FeO 10 g 5 g 15 g Mass of reactants = Mass of products Reactants? Products? Methane + Oxygen Carbon Dioxide + Water CH4 + O2 CO2 + H2O 32 g 128 g 88 g ? THE ELEMENTS 400 BC The Ancient Greeks believed there were 4 elements: Earth, Wind, Fire, Water 2014 AD There are 118 known elements (98 exist naturally) SYMBOLS FOR THE ELEMENTS Each element is represented by an ATOMIC SYMBOL composed of 1-2 letter(s) 1st letter – always capital 2nd letter – always lower case Some symbols come from Latin names You do not need to memorize any atomic symbols, but you must be able to quickly identify them using a Periodic Table Co CO Cobalt Carbon monoxide Sn SN Tin Sulfur & a little Nitrogen FORMULAS OF COMPOUNDS CHEMICAL FORMULA – The representation of a compound or molecule using atomic symbols Writing formulas: 1. Each element present is represented by its atomic symbol 2. A right subscript tells the number of atoms of each element 3. Subscripts of “1” are not written CS2 Na3AsO4 1 carbon atom 3 sodium atoms 2 sulfur atoms 1 arsenic atom 4 oxygen atoms Zn(NO3)2 BaCl22H2O 1 zinc atom 1 barium atom 2 nitrogen atoms 2 chlorine atoms 6 oxygen atoms 4 hydrogen atoms 2 oxygen atoms 400 BC – DEMOCRITUS Proposed that all matter is composed of particles ATOM comes from the Greek Atomos, meaning indivisible 1803 – JOHN DALTON Dalton’s Atomic Theory: 1. All matter is made of atoms 2. All atoms of a given element are the same 3. Atoms can combine in whole number ratios to form compounds 4. Atoms of one element cannot change into atoms of another element Because of Dalton’s atomic theory, most scientists in the 1800’s believed that the atom was a tiny solid ball that could not be broken up into parts. DALTON MODEL OF THE ATOM 1897 – J. J. THOMSON Discovered electrons, indicating that atoms consist of subatomic particles ELECTRONS – Negatively charged subatomic particles PLUM PUDDING MODEL OF THE ATOM 1910 – ERNEST RUTHERFORD Discovered that the atom has a small, positively charged core which contains almost all of the atom’s mass RUTHERFORD MODEL OF THE ATOM NUCLEUS – The dense, positive core of the atom that contains protons PROTONS – Positively charged subatomic particles 1932 – JAMES CHADWICK Discovered a third subatomic particle that is found in the nuclei of atoms NEUTRONS –Neutral subatomic particles NUCLEAR MODEL OF THE ATOM Location Charge Relative Mass Proton Nucleus + 1 Neutron Nucleus 0 1 Electron Around - 1/1836 Nucleus ISOTOPES All atoms of a given element contain the same number of protons ATOMIC NUMBER (Z) – The number of protons in an atoms ← Atomic Number ← Atomic Symbol Since atoms are electrically neutral, the number of electrons equals the number of protons Any atom with 1 proton is a hydrogen atom All 3 are hydrogen atoms because they each have 1 proton ISOTOPES – Atoms of the same element (same number of protons), but with different numbers of neutrons MASS NUMBER (A) – The sum of the protons and neutrons in an atom Protons 1 1 1 Neutrons 0 1 2 Electrons 1 1 1 Mass Number 1 2 3 Nuclide Symbol 1H 2H 3H Isotope Name Hydrogen-1 Hydrogen-2 Hydrogen-3 Mass Numbers ARE NOT found on the Periodic Table Protons 2 2 Neutrons 1 2 Electrons 2 2 Mass Number 3 4 Nuclide Symbol 3He 4He Isotope Name Helium-3 Helium-4 PERIODIC TABLE An arrangement of the chemical elements in order of atomic number, with elements having similar properties placed in columns 1869 – DMITRI MENDELEEV Developed the first periodic table PERIOD or SERIES – A row GROUP or FAMILY – A column Elements in columns have similar properties because they have the same number of valence electrons METALS Physical Properties – Metallic luster, malleable, ductile, conductors of heat and electricity Solids are brilliant white (or silver) except copper (red) and gold (yellow); mercury is a liquid NONMETALS Physical Properties – Opposite of metals Some are crystalline solids, bromine is a liquid, and some are gases METALLOIDS Properties of metals and nonmetals Border the diagonal line separating the metals and nonmetals Hydrogen - A group of its own Group 1 - Alkali Metals Group 2 - Alkaline Earth Metals Group 7 - Halogens Group 8 - Noble Gases Middle Block - Transition Metals Extra Block - Inner Transition Metals (Lanthanides and Actinides) Cu, Ag, Au, Pt - Noble Metals NATURAL STATE OF MATTER Most elements are ACTIVE, so they easily form compounds Matter is mostly a mixture of compounds, not elements INERT elements can be found in their elemental form 1) Noble Metals : Cu, Ag, Au, Pt 2) Noble Gases : He, Ne, Ar, Kr, Xe, Rn To see any other element in its elemental state, compounds must be decomposed METALS In their elemental state, metals consist of billions of atoms bonded together This strong chemical bonding causes most metals to be solids NONMETALS In their elemental state, most nonmetals consist of a small number of atoms bonded together, while a few consist of billions of atoms bonded together Molecules weakly attract, so molecular matter often exists in the gaseous state, but the molecules may attract each other enough to form solids or liquids 7 of the nonmetals that exist as molecules produce DIATOMIC MOLECULES Some elements have several forms in the elemental state 1) Oxygen : dioxygen (O2) and ozone (O3) 2) Carbon : diamond, graphite, buckminsterfullerene ALLOTROPES – Different forms of a given element due to different interatomic bonding Atoms can gain or lose electrons ION – An atom with a positive or negative charge because it has gained or lost electrons Lithium (Z = 3) 3 Protons 3 Protons 3 Electrons 2 Electrons Lithium atom Lithium ion Li Li+ Li → Li+ + e- CATION – A positive ion Cations have the same name as their corresponding atom Cations are created when metals form compounds with nonmetals Fluorine (Z = 9) 9 Protons 9 Protons 9 Electrons 10 Electrons Fluorine atom Fluoride ion F F- F + e- → F- ANION – A negative ion Anions are named with an –ide ending Anions are created when nonmetals form compounds with metals Many ion charges can be predicted from the Periodic Table barium potassium aluminum Ba2+ bromide oxide phosphide Br- NUCLEAR MODEL OF THE ATOM Location Charge Mass Proton Nucleus + 1.67310-27 kg Neutron Nucleus 0 1.67510-27 kg Electron Around - 9.11010-31 kg Nucleus MASS OF PROTON = 0.000000000000000000000000001673kg MASS OF ELECTRON = 0.000000000000000000000000000000911 kg Since subatomic particles are so small, an alternate unit is used to measure mass ATOMIC MASS UNIT (amu or u) – One twelfth the mass of a carbon-12 atom 1 amu = 1 u = 1.6610-27 kg NUCLEAR MODEL OF THE ATOM Location Charge Mass Proton Nucleus + 1.007 u Neutron Nucleus 0 1.009 u Electron Around - 0.0005486 u Nucleus ATOMIC MASS – The mass of an individual atom Hydrogen-1 Hydrogen-2 Hydrogen-3 1.008 u 2.014 u 3.016 u Use a reference table to find the atomic masses of different isotopes To generate these tables, a mass spectrometer was used to measure the atomic masses MASS OF PROTON = 1.007 u 1 u MASS OF NEUTRON = 1.009 u 1 u The mass of a proton or neutron is approximately 1 u Atomic Mass Mass Number Hydrogen-1 Hydrogen-2 Hydrogen-3 1.008 u 2.014 u 3.016 u 1 u 2 u 3 u Each element has many different isotopes (same number of protons, but different numbers of neutrons) Each isotope has a unique atomic mass Hydrogen-1 Hydrogen-2 Hydrogen-3 1.008 u 2.014 u 3.016 u Can an element have a single atomic mass if its isotopes each have different atomic masses??? ← Atomic Number (Z) ← Atomic Symbol ← Atomic Weight (or Average Atomic Mass) ATOMIC WEIGHT– The weighted average of the atomic masses of all of the element’s naturally occurring isotopes The atomic masses of individual isotopes are found in reference tables.