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Inorganic Chemistry, Second Edition

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Instant NotesInorganic ChemistrySecond Edition

The INSTANT NOTES seriesSeries Editor: B.D.Hames School of Biochemistry and Molecular Biology, University of Leeds, Leeds, UKAnimal Biology 2nd editionBiochemistry 2nd editionBioinformaticsChemistry for Biologists 2nd editionDevelopmental BiologyEcology 2nd editionImmunology 2nd editionGenetics 2nd editionMicrobiology 2nd editionMolecular Biology 2nd editionNeurosciencePlant BiologyChemistry seriesConsulting Editor: Howard StanburyAnalytical ChemistryInorganic Chemistry 2nd editionMedicinal ChemistryOrganic Chemistry 2nd editionPhysical ChemistryPsychology seriesSub-series Editor: Hugh Wagner Dept of Psychology, University of Central Lancashire, Preston, UKPsychologyForthcoming titlesCognitive PsychologyPhysiological Psychology

Instant NotesInorganic ChemistrySecond EditionP.A.CoxInorganic Chemistry Laboratory,New College, Oxford, UKLONDON AND NEW YORK

Garland Science/BIOS Scientific Publishers, 2004First published 2000Second edition 2004All rights reserved. No part of this book may be reproduced or transmitted, in any form or by any means, without permission.A CIP catalogue record for this book is available from the British Library.ISBN 0-203-48827-X Master e-book ISBNISBN 0-203-59760-5 (Adobe eReader Format)ISBN 1 85996 289 0Garland Science/BIOS Scientific Publishers4 Park Square, Milton Park, Abingdon, Oxon OX14 4RN, UK and29 West 35th Street, New York, NY 10001–2299, USAWorld Wide Web home page: www.bios.co.ukGarland Science/BIOS Scientific Publishers is a member of the Taylor & Francis GroupThis edition published in the Taylor & Francis e-Library, 2005.“To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go towww.eBookstore.tandf.co.uk.”Distributed in the USA byFulfilment CenterTaylor & Francis10650 Toebben DriveIndependence, KY 41051, USAToll Free Tel.: 1 800 634 7064; E-mail: taylorandfrancis@thomsonlearning.comDistributed in Canada byTaylor & Francis74 Rolark DriveScarborough, Ontario M1R 4G2, CanadaToll Free Tel: 1 877 226 2237; E-mail: tal fran@istar.caDistributed in the rest of the world byThomson Publishing ServicesCheriton House North Way Andover, Hampshire SP10 5BE, UKTel: 44 (0)1264 332424; E-mail: brary of Congress Cataloging-in-Publication DataCox, P.A.Inorganic chemistry/P.A.Cox.—2nd ed.p. cm.—(The instant notes chemistry series)Includes bibliographical references and index.ISBN 1-85996-289-0 (pbk.)1. Chemistry, Inorganic—Outlines, syllabi, etc. I. Title. II. Series.QD153.5.C69 2004 546′.02′02–dc22Production Editor: Andrea Bosher

CONTENTSAbbreviationsPrefaceSection A—viiixAtomic structureA1The nuclear atom2A2Atomic orbitals6A3Many-electron atoms11A4The periodic table15A5Trends in atomic properties19Section B—Introduction to inorganic substancesB1Electronegativity and bond type25B2Chemical periodicity29B3Stability and reactivity33B4Oxidation and reduction37B5Describing inorganic compounds41B6Inorganic reactions and synthesis45B7Methods of characterization49Section C—Structure and bonding in moleculesC1Electron pair bonds55C2Molecular shapes: VSEPR60C3Molecular symmetry and point groups65C4Molecular orbitals: homonuclear diatomics70C5Molecular orbitals: heteronuclear diatomics75C6Molecular orbitals: polyatomics79C7Rings and clusters83C8Bond strengths87

viC9C10Section D—Lewis acids and bases91Molecules in condensed phases94Structure and bonding in solidsD1Introduction to solidsD2Element structures102D3Binary compounds: simple structures106D4Binary compounds: factors influencing structure111D5More complex solids115D6Lattice energies119D7Electrical and optical properties of solids124Section E—98Chemistry in solutionE1Solvent types and properties129E2Brønsted acids and bases133E3Complex formation137E4Solubility of ionic substances141E5Electrode potentials144Section F—Chemistry of nonmetalsF1Introduction to nonmetals149F2Hydrogen152F3Boron156F4Carbon, silicon and germanium160F5Nitrogen164F6Phosphorus, arsenic and antimony168F7Oxygen172F8Sulfur, selenium and tellurium176F9Halogens180Noble gases184F10Section G—Chemistry of non-transition metalsG1Introduction to non-transition metals188G2Group 1: alkali metals192G3Group 2: alkaline earths195G4Group 12: zinc, cadmium and mercury198

viiG5Group 13: aluminum to thallium201G6Group 14: tin and lead205Section H—Chemistry of transition metalsH1Introduction to transition metals209H2Ligand field theory213H33d series: aqueous ions217H43d series: solid compounds220H54d and 5d series223H6Complexes: structure and isomerism226H7Complexes: kinetics and mechanism230H8Complexes: electronic spectra and magnetism233H9Complexes: π acceptor ligands237Organometallic compounds241H10Section I—Lanthanides and actinidesI1Lanthanum and the lanthanides247I2Actinium and the actinides250Section J—Environmental, biological and industrial aspectsJ1Origin and abundance of the elements254J2Geochemistry257J3Bioinorganic chemistry260J4Industrial chemistry: bulk inorganic chemicals265J5Industrial chemistry: catalysts269J6Environmental cycling and pollution273Further reading277The elements 1–103279The Periodic Table of Elements280Index281Appendix I—Appendix II—

Othree-center two-electronthree-center four-electronthree dimensionaladenosine diphosphateactinideatomic orbitaladenosine triphosphatebody-centered cubicbond orderboiling pointconduction bandcubic close packingcoordination numbercyclopentadienyl (C5H5)unspecified (non-metallic) elementelectron affinityeffective atomic numberethylenediamine tetraacetateethyl (C2H5)face-centered cubichexagonal close packinghighest occupied molecular orbitalhard and soft acid-base(first) ionization energynth ionization energy (n 1, 2, )International Union of Pure and Applied Chemistryunspecified ligandlinear combination of atomic orbitalsligand field stabilization energyligand-to-metal charge transferlowest unoccupied molecular orbital

ecified (metallic) elementmethyl (CH3)metal-to-ligand charge transfermolecular orbitalmelting pointphenyl (C6H5)organic group (alkyl or aryl)relative atomic masssteric numberultravioletvalence bandvalence electronvalence shell electron pair repulsionunspecified element (often a halogen)atomic number

PREFACEInorganic chemistry is concerned with the chemical elements (of which there are about 100) and the extremely variedcompounds they form. The essentially descriptive subject matter is unified by some general concepts of structure,bonding and reactivity, and most especially by the periodic table and its underlying basis in atomic structure. As withother books in the Instant Notes series, the present account is intended to provide a concise summary of the core materialthat might be covered in the first and second years of a degree-level course. The division into short independent topicsshould make it easy for students and teachers to select the material they require for their particular course.Sections A–E discuss the general concepts of atomic structure, periodicity, structure and bonding, and solutionchemistry. The following Sections F–I cover different areas of the periodic table in a more descriptive way, although inSection H some concepts that are peculiar to the study of transition metals are also discussed. The final section describessome aspects of inorganic chemistry in the world outside the laboratory.I have assumed a basic understanding of chemical ideas and vocabulary, coming, for example, from an A-levelchemistry course in the UK or a freshman chemistry course in the USA. Mathematics has been kept at a strict minimumin the discussion of atomic structure and bonding. A list of further reading is given for those interested in pursuing theseor other aspects of the subject.In preparing the second edition I have added three extra Topics, on reactions and synthesis, the characterization ofcompounds, and symmetry. A number of corrections and additions have also been made, including new material onnoble gases. These changes aim to strengthen the coverage of synthesis and chemical reactivity, and I hope they willincrease the usefulness of the book as a concise account of the basics of inorganic chemistry.Many people have contributed directly or indirectly to the production of this book. I would particularly like to thankthe following: Howard Stanbury for introducing me to the project; Lisa Mansell and other staff at Garland/BIOS for theirfriendliness and efficiency; the anonymous readers and my colleagues Bob Denning and Jenny Green for their helpfulcomments on the first draft; my students past and present for their enthusiasm, which has made teaching inorganicchemistry an enjoyable task; and Sue for her love and understanding.

Section A—Atomic structure

A1THE NUCLEAR ATOMKey NotesElectrons and nucleiNuclear structureIsotopesRadioactivityRelated topicsAn atom consists of a very small positively charged nucleus, surroundedby negative electrons held by electrostatic attraction. The motion ofelectrons changes when chemical bonds are formed, nuclei beingunaltered.Nuclei contain positive protons and uncharged neutrons. The number ofprotons is the atomic number (Z) of an element. The attractive stronginteraction between protons and neutrons is opposed by electrostaticrepulsion between protons. Repulsion dominates as Z increases and thereis only a limited number of stable elements.Isotopes are atoms with the same atomic number but different numbers ofneutrons. Many elements consist naturally of mixtures of isotopes, withvery similar chemical properties.Unstable nuclei decompose by emitting high-energy particles. Allelements with Z 83 are radioactive. The Earth contains some long-livedradioactive elements and smaller amount of short-lived ones.Actinium and the actinides (I2)Origin and abundance of theelements (J1)Electrons and nucleiThe familiar planetary model of the atom was proposed by Rutherford in 1912 following experiments by Geiger andMarsden showing that nearly all the mass of an atom was concentrated in a positively charged nucleus. Negativelycharged electrons are attracted to the nucleus by the electrostatic force and were considered by Rutherford to‘orbit’ it in a similar way to the planets round the Sun. It was soon realized that a proper description of atoms requiredthe quantum theory; although the planetary model remains a useful analogy from the macroscopic world, many of thephysical ideas that work for familiar objects must be abandoned or modified at the microscopic atomic level.The lightest atomic nucleus (that of hydrogen) is 1830 times more massive than an electron. The size of a nucleus isaround 10 15 m (1 fm), a factor of 105 smaller than the apparent size of an atom, as measured by the distances betweenatoms in molecules and solids. Atomic sizes are determined by the radii of the electronic orbits, the electron itselfhaving apparently no size at all. Chemical bonding between atoms alters the motion of electrons, the nuclei remainingunchanged. Nuclei retain the ‘chemical identity’ of an element, and the occurrence of chemical elements depends onthe existence of stable nuclei.

A1–THE NUCLEAR ATOM3Nuclear structureNuclei contain positively charged protons and uncharged neutrons; these two particles with about the same mass areknown as nucleons. The number of protons is the atomic number of an element (Z), and is matched in a neutralatom by the same number of electrons. The total number of nucleons is the mass number and is sometimes specifiedby a superscript on the symbol of the element. Thus 1H has a nucleus with one proton and no neutrons, 16O has eightprotons and eight neutrons, 208Pb has 82 protons and 126 neutrons.Protons and neutrons are held together by an attractive force of extremely short range, called the stronginteraction. Opposing this is the longer-range electrostatic repulsion between protons. The balance of the two forcescontrols some important features of nuclear stability. Whereas lighter nuclei are generally stable with approximately equal numbers of protons and neutrons, heavier oneshave a progressively higher proportion of neutrons (e.g. compare 16O with 208Pb). As Z increases the electrostatic repulsion comes to dominate, and there is a limit to the number of stable nuclei, allelements beyond Bi (Z 83) being radioactive (see below).As with electrons in atoms, it is necessary to use the quantum theory to account for the details of nuclear structure andstability. It is favorable to ‘pair’ nucleons so that nuclei with even numbers of either protons or neutrons (or both) aregenerally more stable than ones with odd numbers. The shell model of nuclei, analogous to the orbital picture of atoms(see Topics A2 and A3) also predicts certain magic numbers of protons or neutrons, which give extra stability. Theseare16Oand 208Pb are examples of nuclei with magic numbers of both protons and neutrons.Trends in the stability of nuclei are important not only in determining the number of elements and their isotopes (seebelow) but also in controlling the proportions in which they are made by nuclear reactions in stars. These determine theabundance of elements in the Universe as a whole (see Topic J1).IsotopesAtoms with the same atomic number and different numbers of neutrons are known as isotopes. The chemicalproperties of an element are determined largely by the charge on the nucleus, and different isotopes of an element havevery similar chemical properties. They are not quite identical, however, and slight differences in chemistry and inphysical properties allow isotopes to be separated if desired.Some elements have only one stable isotope (e.g. 19F, 27Al, 31P), others may have several (e.g. 1H and 2H, the latteralso being called deuterium, 12C and 13C); the record is held by tin (Sn), which has no fewer than 10. Natural samplesof many elements therefore consist of mixtures of isotopes in nearly fixed proportions reflecting the ways in which thesewere made by nuclear synthesis. The molar mass (also known as relative atomic mass, RAM) of elements isdetermined by these proportions. For many chemical purposes the existence of such isotopic mixtures can be ignored,although it is occasionally significant. Slight differences in chemical and physical properties can lead to small variations in the isotopic composition ofnatural samples. They can be exploited to give geological information (dating and origin of rocks, etc.) and lead tosmall variations in the molar mass of elements.

4SECTION A–ATOMIC STRUCTURE Some spectroscopic techniques (especially nuclear magnetic resonance, NMR, see Topic B7) exploit specificproperties of particular nuclei. Two important NMR nuclei are 1H and 13C. The former makes up over 99.9% ofnatural hydrogen, but 13C is present as only 1.1% of natural carbon. These different abundances are important bothfor the sensitivity of the technique and the appearance of the spectra. Isotopes can be separated and used for specific purposes. Thus the slight differences in chemical behavior betweennormal hydrogen (1H) and deuterium (2H) can be used to investigate the detailed mechanisms of chemical reactionsinvolving hydrogen atoms.In addition to stable isotopes, all elements have unstable radioactive ones (see below). Some of these occur naturally,others can be made artificially in particle accelerators or nuclear reactors. Many radioactive isotopes are used inchemical and biochemical research and for medical diagnostics.RadioactivityRadioactive decay is a process whereby unstable nuclei change into more stable ones by emitting particles of differentkinds. Alpha, beta and gamma (α, β and γ) radiation was originally classified according to its different penetratingpower. The processes involved are illustrated in Fig. 1. An α particle is a 4He nucleus, and is emitted by some heavy nuclei, giving a nucleus with Z two units less and massnumber four units less. For example, 238U (Z 92) undergoes a decay to give (radioactive) 234Th (Z 90). A β particle is an electron. Its emission by a nucleus increases Z by one unit, but does not change the mass number.Thus 14C (Z 6) decays to (stable) 14N (Z 7). γ radiation consists of high-energy electromagnetic radiation. It often accompanies α and β decay.Fig. 1. The 238U decay series showing the succession of α and β decay processes that give rise to many other radioactive isotopes and end with stable206Pb.

A1–THE NUCLEAR ATOM5Some other decay processes are known. Very heavy elements can decay by spontaneous fission, when the nucleussplits into two fragments of similar mass. A transformation opposite to that in normal β decay takes place either byelectron capture by the nucleus, or by emission of a positron (β ) the positively charged antiparticle of an electron.Thus the natural radioactive isotope 40K (Z 19) can undergo normal β decay to 40Ca (Z 20), or electron capture togive 40Ar (Z 18).Radioactive decay is a statistical process, there being nothing in any nucleus that allows us to predict when it willdecay. The probability of decay in a given time interval is the only thing that can be determined, and this appears to beentirely constant in time and (except in the case of electron capture) unaffected by temperature, pressure or thechemical state of an atom. The probability is normally expressed as a half-life, the time taken for half of a sample todecay. Half-lives can vary from a fraction of a second to billions of years. Some naturally occurring radioactive elementson Earth have very long half-lives and are effectively left over from the synthesis of the elements before the formation ofthe Earth. The most important of these, with their half-lives in years, are 40K (1.3 109), 232Th (1.4 1010) and 238U (4.5 109).The occurrence of these long-lived radioactive elements has important consequences. Radioactive decay gives a heatsource within the Earth, which ultimately fuels many geological processes including volcanic activity and long-termgeneration and movement of the crust. Other elements result from radioactive decay, including helium and argon andseveral short-lived radioactive elements coming from the decay of thorium and uranium (see Topic I2). Fig. 1 showshow 238U decays by a succession of radioactive α and β processes, generating shorter-lived radioactive isotopes of otherelements and ending as a stable isotope 206Pb of lead. Similar decay series starting with 232Th and 235U also generateshort-lived radioactive elements and end with the lead isotopes 208Pb and 207Pb, respectively.All elements beyond bismuth (Z 83) are radioactive, and none beyond uranium (Z 92) occur naturally on Earth. Withincreasing numbers of protons heavier elements have progressively less stable nuclei with shorter half-lives. Elementswith Z up to 110 have been made artificially but the half-lives beyond Lr (Z 103) are too short for chemicalinvestigations to be feasible. Two lighter elements, technetium (Tc, Z 43) and promethium (Pm, Z 61), also have nostable isotopes.Radioactive elements are made artificially by bombarding other nuclei, either in particle accelerators or with neutronsin nuclear reactors (see Topic I2). Some short-lived radioactive isotopes (e.g. 14C) are produced naturally in smallamounts on Earth by cosmic-ray bombardment in the upper atmosphere.

Section A—Atomic structureA2ATOMIC ORBITALSKey NotesWavefunctionsQuantum number andnomenclatureAngular functions:‘shapes’Radical distributonsEnergies in hydrogenHydrogenic ionsRelated topicsThe quantum theory is necessary to describe electrons. It predictsdiscrete allowed energy levels and wavefunctions, which giveprobability distributions for electrons. Wavefunctions for electrons inatoms are called atomic orbitals.Atomic orbit

Analytical Chemistry Inorganic Chemistry 2nd edition Medicinal Chemistry Organic Chemistry 2nd edition Physical Chemistry . Section E— Chemistry in solution E1 Solvent types and properties 129 . The following Sections F–I cover different areas of the periodic table in a more descriptive way, although in .