DOCSLIB.ORG

Introduction to Inorganic Chemistry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Introduction to Inorganic Chemistry Introduction to Inorganic Chemistry What is inorganic chemistry? Inorganic Chemistry Organimetallic Bioinorganic Organic vs Inorganic Introduction to Inorganic Chemistry Organic vs Inorganic Introduction to Inorganic Chemistry Organic vs Inorganic Chapter 8 An Introduction to Coordination Compounds Constitution and geometry 8.1 Low coordination numbers 8.2 Intermediate coordination numbers 8.1 High coordination numbers 8.4 Polymetallic complexes Ligands and nomenclature 8.5 Representative ligands 8.6 Nomenclature Isomerism and chirality 8.7 Square-planar complexes 8.8 Tetrahedral complexes 8.9 Trigonal-bipyramidal and square-pyramidal complexes 8.10 Octahedral complexes 8.11 Ligand chirality History What is coordination compound? Coordination compounds include compound composed of a metal atom or ion and one or more ligands that formally donate electrons to the metal. More specifically, a transition metal surrounded by neutral molecules or anions with a definite geometry. What is ligand? Ligand can be a atom, ion, and molecules. Prussian blueHistory(German: Preußischblau or Berliner Blau, in English Berlin blue) is a dark blue pigment used in paints and formerly in blueprints. Prussian blue was discovered by accident by painter Heinrich Diesbach in Berlin in 1704-5,What which is is coordinationwhy it is also known compound? as Berlin blue. (Diesbach was Coordinationattempting to complexescreate a paint were with known a red - hue.) although It has not several understood different chemicalin any names, sense these- since being the begi iron(III)nning ferrocyanide, of chemistry, ferric e.g. ferrocyanide,Prussian iron(III)blue hexacyanoferrate(II),, Aureolin, and copper and vitriol ferric. hexacyanoferrate. Commonly and conveniently it is simply called "PB. The key breakthrough occurred when Alfred Werner proposed, Aureolininter alia(sometimes, that Co(III) called bears Cobalt six ligands Yellow in) isan a octahedralpigment used geometry. in oil and watercolor painting. Its color index name is PY40 (40th entry on list of yellow pigments). It was first made in 1851 and its chemical composition is potassium cobaltinitrite. Copper(II) sulfate ("sulphate" in most Commonwealth nations) is the chemical compound with the formula CuSO4. This salt exists as a series of compounds that differ in their degree of hydration. The anhydrous form is a pale green or gray-white powder, while the pentahydrate, the most commonly encountered salt, is bright blue. This hydrated copper sulfate occurs in nature as the mineral called chalcanthite. The archaic name for copper(II) sulfate is "blue vitriol" or "bluestone" Nobel Prize for Chemistry Alfred Werner 1913 For complexes with more than one type of ligand, Werner succeeded in Inexplaining 1893, Werner the number was the of firstisomers to proposobserved.e correct For structuresexemple, hefor explained coordination the compoundsexistence of containingtwo isomers complex of "Co(NH ions3), 4inCl which3", one a green central and transition one purple. metal atomWerner is surroundedproposed that by theseneutral are or two anionic geometric ligands isomers. of formula - For[Co(NH example,3)4Cl2]Cl, it was with known one Cl thation coba dissociatedlt forms aas "complex" confirmed with by conductivityformula measurements. The Co atom is surrounded by four NH and two Cl ligands CoCl3•6NH3, but the nature of the association indicated3 by the dot was at the vertices of an octahedron. The green isomer is "trans" with the two mysterious. Werner proposed the structure [Co(NH3)6]Cl3, with the Co3+ Cl ligands at opposite vertices, and the purple is "cis" with the two Cl at ion surrounded by six NH3 at the vertices of an octahedron. The three Cl- areadjacent dissociated vertices. as free ions, which he confirmed by measuring the electrical conductivity of the compound in aqueous solution. History What is coordination compound? Coordination complexes were known - although not understood in any sense - since the beginning of chemistry, e.g. Prussian blue, Aureolin, and copper vitriol. The key breakthrough occurred when Alfred Werner proposed, inter alia, that Co(III) bears six ligands in an octahedral geometry. The theory allows one to understand the difference between coordinated and ionic chloride in the cobalt ammine chlorides and to explain many of the previously inexplicable isomers. He resolved the first coordination complex into optical isomers, overthrowing the theory that chirality was necessarily associated with carbon compounds. History What is ligand? In chemistry, a ligand is an atom, ion, or molecule that generally donates one or more of its electrons through a coordinate covalent bond to one or more central atoms or ions (these ligands act as a Lewis base). The ligands that are directly bonded to the metal (that is, share electrons), are called "inner sphere" ligands. If the inner-sphere ligands do not balance the charge of the central atom, this may be done by simple ionic bonding with another set of counter ions (the "outer-sphere" ligands). The complex of the metal with the inner sphere ligands is then called a complex ion (which can be either cationic or anionic). The complex, along with its counter ions, is called a coordination compound. The size of a ligand is indicated by its cone angle. History Organometallic Compound Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Organometallic chemistry combines aspects of inorganic chemistry and organic chemistry. Organometallic compounds find practical use in stoichiometric and catalytically active compounds. Electron counting is key in understanding organometallic chemistry. The 18-electron rule is helpful in predicting the stabilities of organometallic compounds. Organometallic compounds which have 18 electrons (filled s, p, and d orbitals) are relatively stable. This suggests the compound is isolable, but it can result in the compound being inert. Nomenclature – Common Monodentate Ligands Classical (or "Werner Complexes"): Ligands in classical coordination chemistry bind to metals. Organometallic: Ligands are organic (alkenes, alkynes, alkyls) as well as "organic-like" ligands such as phosphines, hydride, and CO. Bioinorganic: Ligands are those provided by nature, especially including the side chains of amino acids, and many cofactors such as porphyrins. Example: hemoglobin Cluster: Ligands are all of the above but also include other metals as ligands. Example Ru3(CO)12 Constitution and geometry In an inner-sphere complex, the ligands are attached directly to a central metal ion: the number of ligands depends on the size of the metal, the identity of the ligands, and the electronic interactions. 2+ 2- Size: ligand, central atom or ion {[Mn(H2O)6] SO4 } vs Electron density [Mn(H2O)5SO4] Multiple bond Constitution and geometry 8.1 Low coordination numbers Coordination number 2; Cu+, Ag+, Au+, they often gain additional ligands to form three- or four- coordinate complexes. Coordination number 3: with bulky ligands Position of these complexes in periodic table. Constitution and geometry 8.2 Intermediate coordination numbers Coordination number 4, 5, 6. They include the vast majority of complexes. Four-coordination: Tetrahedral complexes are favoured over higher coordinate complexes if the central atom is small or the ligands large. - ligand-ligand repulsions override the energy advantage of forming more metal-ligand bonds Square-planar complexes are typically observed for metals with d8 configurations (Rh+, Ir+, Pd2+, Pt2+, Au3+). Constitution and geometry 8.2 Intermediate coordination numbers Geometric isomerism Constitution and geometry 8.2 Intermediate coordination numbers Five-coordination: The energies of the various geometries of five-coordinate complexes differ little from one another and such complexes are often fluxional. Square pyramidal or trigonal bipyramidal. Distortions from these ideal geometries are common. Constitution and geometry 8.2 Intermediate coordination numbers Berry pseudorotation [Fe(CO)5]; crystal, NMR, IR Constitution and geometry 8.2 Intermediate coordination numbers Six-coordination: Octahedral; the most common arrangement, highly symmetric structure. Distortion Trigonal-prismatic distortion Constitution and geometry 8.3 Higher coordination numbers Larger atoms and ions, particularly those of the f block, tend to form complexes with high coordination number. Seven-coordination; pentagonal bipyramid, cpped octahedron, capped trigonal prism – a number of intermediate structures. Eight-coordination; square antiprismatic, dodecahedral, cubic. Nine-coordination; Ten- and twelve-coordination Constitution and geometry 8.4 Polymetallic complexes Metal cluster; contain M-M Cage complex; contain ligand-bridged atoms Ligands and nomenclature 8.5 Representative ligands Chelate Bite angel Six-membered rings may be favoured sterically or by electron delocalization through their pi-orbitals Monodentate, bidentate, tridentate…. Ambidentate; Thiocyanate ion (NCS-) – isothiocyanato complex (attach via N atom), thiocyanato complexes (attach via S atom). - Nitrite ion (NO2 ) – nitro, nitrito Constitution and geometry 8.4 Polymetallic complexes Constitution and geometry 8.4 Polymetallic complexes.
Load more

Recommended publications
  • General Inorganic Chemistry
    General Inorganic Chemistry Pre DP Chemistry Period 1 • Teacher: Annika Nyberg • [email protected] • Urgent messages via Wilma! Klicka här för att ändra format på underrubrik i bakgrunden • Course book: • CliffsNotes: Chemistry Quick Review http://www.chem1.com/acad/webtext/virtualtextbook.html Content • Introduction • The Structure of Matter (Chapter 1) • The Atom (Chapter 2 and 3) • Chemical bonding (Chapter 5) • The Mole (Chapter 2) • Solutions (Chapter 9) • Acids and bases (Chapter 10) • Quiz • Revision • EXAM 9.00-11.45 Assessment Exam: 80 % Quiz: 20% + practical work, activity and absences 1. Chemistry: a Science for the twenty-first century ● Chemistry has ancient roots, but is now a modern and active, evolving science. ● Chemistry is often called the central science, because a basic knowledge of chemistry is essential for students in biology, physics, geology and many other subjects. https://www.youtube.com/watch?v=tTlnrhiadnI ● Chemical research and development has provided us with new substances with specific properties. These substances have improved the quality of our lives. Health and medicine vaccines sanitation systems antibiotics anesthesia and all other drugs Energy new alternative energy sources (e.g. solar energy to electric energy, nuclear fission) electric cars with long lasting batteries Environment greenhouse gases acid rain and smog Materials and Technology ● polymers (rubber and nylon), ceramics (cookware), liquid crystals (electronic displays), adhesives (Post-It notes), coatings (latex-paint), silicon chips (computers) Food and Agriculture substances for biotechnology ● The purpose of this course is to make you understand how chemists see the world. ● In other words, if you see one thing (in the macroscopic world) you think another (visualize the particles and events in the microscopic world).
    [Show full text]
  • Basic Chemistry
    CH 2- THE CHEMISTRY OF LIFE Atoms . The study of chemistry begins with the basic unit of matter, the atom. The Greek philosopher Democritus called the smallest fragment of matter the atom, from the Greek word atomos. Atoms (cont.) . Placed side by side, 100 million atoms would make a row only about 1 centimeter long. Atoms contain subatomic particles that are even smaller. Atoms (cont.) . What three subatomic particles make up atoms? Atoms (cont.) . The subatomic particles that make up atoms are . protons . neutrons . electrons Atoms (cont.) . Smallest property of an element that still has the properties of that element . “The building blocks of matter” . Atoms are made of smaller (subatomic) particles arranged in a particular way . p+ (proton) . n° (neutron) . e- (electron) Atoms (cont.) . Protons and neutrons have about the same mass. Protons are positively charged particles (+). Neutrons carry no charge (◦). Strong forces bind protons and neutrons together to form the nucleus, which is at the center of the atom. Atoms (cont.) . The electron is a negatively charged particle (−) with 1/1840 the mass of a proton. Electrons are in constant motion in the space surrounding the nucleus (e- cloud). Atoms (cont.) . The subatomic particles in a helium atom. Atoms (cont.) • Electrons are attracted to the positively charged nucleus but remain outside the nucleus because of the energy of their motion. • Because atoms have equal numbers of electrons and protons, and because these subatomic particles have equal but opposite charges, atoms are neutral. Atoms (cont.) . Atomic number- # of p+ AND electrons in an atom . Mass number- total # of p+ + n° in an atom .
    [Show full text]
  • All About the Chemical Bonds and Compounds
    All about the Chemical Bonds and Compounds Video Transcript Almost everything we see or touch in daily life – such as the food we eat, the water we drink, the air we breathe, and so on – is the result of chemical bonding. In other words, the world around us is generally not composed of isolated atoms. Instead, atoms bond to one another to form molecules and hence chemical compounds, which make up the world around us. Chemical bonding is the physical process that causes atoms and molecules to be attracted to each other and held together in more stable chemical compounds. There are three primary types of chemical bonds and compounds: Ionic bonds, covalent bonds, and metallic bonds. With ionic bonds, electrons are exchanged or transferred between atoms. They exist in ionic compounds. Generally, they’re a metal and a nonmetal – sodium chloride, magnesium oxide, etc. With covalent bonds, electrons are shared among the atoms. They exist in covalent and molecular compounds. Generally, they are nonmetals – carbon dioxide, dihydrogen monoxide, etc. With metallic bonds, a pool of electrons roam freely across entire molecule. They exist in metallic compounds. Generally, they’re metals and alloys – copper, gold, etc. A chemical compound is a group of two or more different atoms that are attracted to each other. Compounds can be divided into ionic compounds, covalent compounds, and metallic compounds. This table lists some key properties of each. Be aware that it is the valence electrons (those in the outermost level) that are involved in bonding. Atoms try to fill their outer energy levels because it’s energetically favorable for atoms to be in that configuration and it makes them stable.
    [Show full text]
  • Chemical Formula
    Chemical Formula Jean Brainard, Ph.D. Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required) AUTHOR Jean Brainard, Ph.D. To access a customizable version of this book, as well as other interactive content, visit www.ck12.org CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the FlexBook®, CK-12 intends to pioneer the generation and distribution of high-quality educational content that will serve both as core text as well as provide an adaptive environment for learning, powered through the FlexBook Platform®. Copyright © 2013 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Com- mons from time to time (the “CC License”), which is incorporated herein by this reference.
    [Show full text]
  • Chapter 10 – Chemical Reactions Notes
    Chapter 8 – Chemical Reactions Notes Chemical Reactions: Chemical reactions are processes in which the atoms of one or more substances are rearranged to form different chemical compounds. How to tell if a chemical reaction has occurred (recap): Temperature changes that can’t be accounted for. o Exothermic reactions give off energy (as in fire). o Endothermic reactions absorb energy (as in a cold pack). Spontaneous color change. o This happens when things rust, when they rot, and when they burn. Appearance of a solid when two liquids are mixed. o This solid is called a precipitate. Formation of a gas / bubbling, as when vinegar and baking soda are mixed. Overall, the most important thing to remember is that a chemical reaction produces a whole new chemical compound. Just changing the way that something looks (breaking, melting, dissolving, etc) isn’t enough to qualify something as a chemical reaction! Balancing Equations Notes: Things to keep in mind when looking at the recipes for chemical reactions: 1) The stuff before the arrow is referred to as the “reactants” or “reagents”, and the stuff after the arrow is called the “products.” 2) The number of atoms of each element is the same on both sides of the arrow. Even though there may be different numbers of molecules, the number of atoms of each element needs to remain the same to obey the law of conservation of mass. 3) The numbers in front of the formulas tell you how many molecules or moles of each chemical are involved in the reaction. 4) Equations are nothing more than chemical recipes.
    [Show full text]
  • 1 5. Chemical Bonding
    5. Chemical Bonding: The Covalent Bond Model 5.1 The Covalent Bond Model Almost all chemical substances are found as aggregates of atoms in the form of molecules and ions produced through the reactions of various atoms of elements except the noble-gas elements which are stable mono-atomic gases. Chemical bond is a term that describes the attractive force that is holding the atoms of the same or different kind of atoms in forming a molecule or ionic solid that has more stability than the individual atoms. Depending on the kinds of atoms participating in the interaction there seem to be three types of bonding: Gaining or Losing Electrons: Ionic bonding: Formed between many ions formed by metal and nonmetallic elements. Sharing Electrons: Covalent bonding: sharing of electrons between two atoms of non-metals. Metallic Bonding: sharing of electrons between many atoms of metals. Ionic Compounds Covalent Compounds Metallic Compounds 1. Metal and non-meal Non-metal and non-meal Metal of one type or, element combinations. elements combinations. combinations of two or metal elements combinations. 2. High melting brittle Gases, liquids, or waxy, low Conducting, high melting, crystalline solids. melting soft solids. malleable, ductile crystalline solids. 3. Do not conduct as a solid Do not conduct electricity at Conduct electricity at solid but conducts electricity any state. and molten states. when molten. 4. Dissolved in water produce Most are soluble in non-polar Insoluble in any type of conducting solutions solvents and few in water. solvents. (electrolytes) and few These solutions are non- are soluble in non-polar conducting (non- solvents.
    [Show full text]
  • A Science That Studies the Composition and Properties of Matter. 1. Matter
    Chemistry Basics I. Intro A. Chemistry Def- a science that studies the composition and properties of matter . 1. matter- anything that takes up space and has mass. B. Basic Terms: 1. Atom: neutral particle having one nucleus; the smallest representative sample of an element. In other words it is the base building block, of an element. 2. Element: a substance in which all of the atoms have the same atomic number. A substance that cannot be broken down by chemical reactions into anything that is both stable and simpler. Furthermore, all the atoms within an element have the same number of protons. 3. Molecule: a neutral particle composed of two or more atoms combined in a definite ratio of whole numbers. 4. Compound: a substance consisting of chemically combined atoms from two or more elements and present in a definite ratio.( Oxygen mass is always 8 times that of hydrogen) 5. Physical property: a property that can be observed without changing the chemical makeup of a substance. (eg. Color) Is melting point one? 6. Chemical reaction: chemicals, starting materials (reactants), interact with each other resulting in other substances, ending materials (products), with different properties. 7. Chemical Property: The ability of a substance, either by itself or with other substances, to undergo a change into new substances. 8. Extensive Property: a property that depends on sample size.(Volume) 9. Intensive Property: properties independent of size. ( Color, electrical conductivity, melting point…) 10. Pure substance: a substance that is always the same, regardless of its source. 11. Mixtures: a physical combination of elements or compounds that has no particular proportion by mass.
    [Show full text]
  • A Revolution That Never Happened
    Studies in History and Philosophy of Science 49 (2015) 80e90 Contents lists available at ScienceDirect Studies in History and Philosophy of Science journal homepage: www.elsevier.com/locate/shpsa A Revolution that never happened Ursula Klein Max Planck Institute for the History of Science, Germany article info abstract Article history: If we define scientific revolutions as changes of scientists’ ontologies, types of causal explanation, and Available online 19 December 2014 paradigmatic types of methods and instruments, Antoine-Laurent Lavoisier’s contribution to chemistry did not amount to a scientific revolution. Contrary to the received view that Lavoisier initiated a Keywords: “chemical revolution,” which is accepted by Chang and Kusch, I argue that Lavoisier shared with the Chemical revolution; phlogistonists their “flat ontology” of chemical substance, established decades before the 1770s, their Ontology of substances; types of explaining chemical transformation, and their quantitative methods. Based on my historical Elements; reconstruction, I criticize Chang’s argument that the late eighteenth-century phlogistic systems and Mixts; ’ Chemical compounds; Lavoisier s system belonged to two different theoretical traditions. As a consequence, I also question ’ ’ Affinity Chang s argument that the acceptance of Lavoisier s system can be explained in terms of dominance of “compositionism” over “principlism.” Ó 2014 Elsevier Ltd. All rights reserved. When citing this paper, please use the full journal title Studies in History and Philosophy of Science 1. Introduction following the path to Lavoisier’s system, I will compare the phlo- gistic and the antiphlogistic system from a broader historical and As is well known, Thomas Kuhn highlighted Lavoisier’s “chem- philosophical perspective.
    [Show full text]
  • Introduction to Chemistry
    Introduction to Chemistry Author: Tracy Poulsen Digital Proofer Supported by CK-12 Foundation CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook Introduction to Chem... materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based Authored by Tracy Poulsen collaborative model termed the “FlexBook,” CK-12 intends to pioneer the generation and 8.5" x 11.0" (21.59 x 27.94 cm) distribution of high-quality educational content that will serve both as core text as well as provide Black & White on White paper an adaptive environment for learning. 250 pages ISBN-13: 9781478298601 Copyright © 2010, CK-12 Foundation, www.ck12.org ISBN-10: 147829860X Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made Please carefully review your Digital Proof download for formatting, available to Users in accordance with the Creative Commons Attribution/Non-Commercial/Share grammar, and design issues that may need to be corrected. Alike 3.0 Unported (CC-by-NC-SA) License (http://creativecommons.org/licenses/by-nc- sa/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), We recommend that you review your book three times, with each time focusing on a different aspect. which is incorporated herein by this reference. Specific details can be found at http://about.ck12.org/terms. Check the format, including headers, footers, page 1 numbers, spacing, table of contents, and index. 2 Review any images or graphics and captions if applicable.
    [Show full text]
  • Chemical Compounds - Vocabulary
    CHEMICAL COMPOUNDS - VOCABULARY COVALENT COMPOUND A compound that has only covalent bonds between atoms of which it is made. The covalent bond results from sharing valence electrons between two atoms. The representative unit of a covalent compound is usually a molecule. IONIC COMPOUND A compound that is built of monatomic or polyatomic ions of opposite charges. The bonds between ions of opposite charges are called ionic bonds. Many, but not all ionic compounds contain a metallic element. The representative unit of an ionic compound is always a formula unit. There no molecules in ionic compounds. Ions per se are not compounds. FORMULA UNIT The smallest combination of atoms or ions that correctly represents the ratio in which they are combined in a chemical compound. Formula unit is a more general term than a molecule. ORGANIC COMPOUND A compound that is built of atoms of carbon and other elements (most commonly, hydrogen, nitrogen, oxygen, sulfur, and halogens) except for carbon monoxide, carbon dioxide, carbonic acid, carbonates, and hydrogen carbonates. If there is no carbon present, a compound is certainly inorganic. The simplest organic compound is CH4, methane. BINARY COMPOUND Ionic or covalent compound that is made of atoms of two different elements. Examples: MgCl2; Al2O3; HCl; H2O; CH4. DIATOMIC MOLECULE A molecule that is built of exactly two atoms either of the same element or of two different elements. Examples: O2; N2; CO; HF. MONATOMIC ION A single atom that lost or gained one or more electrons as compared to the neutral atom of the same element. The electric charge must be indicted when a formula of it is written unless the ion is combined with another ion in the formula of an ionic compound.
    [Show full text]
  • 2: Alkanes and Cycloalkanes
    (2/94)(1,2,8/95)(6,7/97)(10/98)(1,9-11/99) Neuman Chapter 2 2: Alkanes and Cycloalkanes Alkanes Alkane Systematic Nomenclature Cycloalkanes Conformations of Alkanes Conformations of Cycloalkanes Conformations of Alkylcyclohexanes Preview You learned in the Chapter 1 that all organic molecules have carbon skeletons. These carbon skeletons show great diversity in the ways that C atoms bond to each other, and in their three-dimensional shapes. Alkanes and cycloalkanes consist entirely of carbon skeletons bonded to H atoms since they have no functional groups. As a result, they serve as a basis for understanding the structures of all other organic molecules. This chapter describes the skeleltal isomerism of alkanes and cycloalkanes, their three-dimensional conformations, and their systematic nomenclature that is the basis for the names of all other organic compounds. 2.1 Alkanes We refer to alkanes as hydrocarbons because they contain only C (carbon) and H (hydrogen) atoms. Since alkanes are the major components of petroleum and natural gas, they often serve as a commercial starting point for the preparation of many other classes of organic molecules. Structures of Alkanes (2.1A) Organic chemists use a variety of different types of structures to represent alkanes such as these shown for methane (one C), ethane (two C's), and propane (three C's). [graphic 2.1] Kekulé, Electron-Dot and Three-Dimensional Structures. The structures showing C and H atoms connected by lines are Kekulé structures. Remember from Chapter 1 that these lines represent chemical bonds that are pairs of electrons located in molecular orbitals encompassing the two bonded atoms.
    [Show full text]
  • Chemical Formulas the Elements
    Chemical Formulas A chemical formula gives the numbers and types of atoms that are found in a substance. When the substance is a discrete molecule, then the chemical formula is also its molecular formula. Fe (iron) is a chemical formula Fe2O3 is a molecular formula The Elements The chemical formulas of most of the elements are simply their elemental symbol: Na (sodium) Fe (iron) He (helium) U (uranium) These chemical formulas are said to be monatomic—only an atom in chemical formula 1 The Elements There are seven elements that occur naturally as diatomic molecules—molecules that contain two atoms: H2 (hydrogen) N2 (nitrogen) O2 (oxygen) F2 (fluorine) Cl2 (chlorine) Br2 (bromine) I2 (iodine) The last four elements in this list are in the same family of the Periodic Table Binary Compounds A binary compound is one composed of only two different types of atoms. Rules for binary compound formulas 1. Element to left in Periodic Table comes first except for hydrogen: KCl PCl3 Al2S3 Fe3O4 2 Binary Compounds 2. Hydrogen comes last unless other element is from group 16 or 17: LiH, NH3, B2H4, CH4 3. If both elements are from the same group, the lower element comes first: SiC, BrF3 Other Compounds For compounds with three or more elements that are not ionic, if it contains carbon, this comes first followed by hydrogen. Other elements are then listed in alphabetical order: C2H6O C4H9BrO CH3Cl C8H10N4O2 3 Other Compounds However, the preceding rule is often ignored when writing organic formulas (molecules containing carbon, hydrogen, and maybe other elements) in order to give a better idea of how the atoms are connected: C2H6O is the molecular formula for ethanol, but nobody ever writes it this way—instead the formula is written C2H5OH to indicate one H atom is connected to the O atom.
    [Show full text]