Chemical Structure and Bonding

354 Pages·1989·14.511 MB·English

by  Roger L. Dekock, Harry B. Gray

ChemicaSl tructurea ndB ondin·g
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RogerL . DeKock
CalvinC ollege
HarryB . Gray
CaliforniaIn stituteo f Technology
UNIVERSITSYC IENCEB OOKS
SausalitoC, allfornla
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Chemistry Library C ' ' , ;, I. I ~/ , L 'I- f
University Science Books
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Sausalito, CA 94965
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Cover designer: Bob Ishi
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Copyright© 1989 by University Science Books
Reproduction or translation of any part of this work beyond that
permitted by Section 107 or 108 of the 1976 United States Copyright Act
without the permission of the copyright owner is unlawful. Requests for
permission or further information should be addressed to the Permissions
Department, University Science Books.
Library of Congress Catalog Number: 89-050820
ISBN 0-935702-61-X
Printed in the United States of America
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Prefacet o the SecondE dition C DP'j: 2
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With this paperback edition, University Science Books becomes the publisher of
ChemicalS tructure andB onding.W e thank the publisher, Bruce Armbruster, for
his interest in chemistry and chemistry education.
Roger L. DeKock
Harry B. Gray
I.,
Prefacet o the First Edition
Chemical Structure and Bonding was written for courses devoted specifi
cally to structure and bonding topics, and for courses in inorganic, physical,
and quantum chemistry whose subject matter significantly involves these
topics. We hope that for many undergraduate students, this textbook will
be the first serious introduction to the concepts of structure and bonding.
In addition, graduate students and others should find our treatment of these
topics to be a helpful review. We have included numerous questions and
problems at the end of each chapter and an Appendix with answers to most
of the problems. The manuscript is without footnotes to the original litera
ture, but for those who wish to pursue further reading and study, a "Sugges
tions for Further Reading" section is provided at the end of each chapter.
We have written Chemical Structure and Bonding so as to provide the
flexibility of subject matter that instructors often require. For example, an
instructor who wished to concentrate on molecular orbital theory could use
mainly Chapters 4, 5, and 6. Alternatively, a course that was designed to
cover several of the topics only briefly could omit those sections considered
unnecessary or too advanced.
The coverage of material in this textbook is purposely broad. Chapter 1
starts with the elementary Bohr theory and proceeds to the quantum theory
of Schrodinger and its application to the particle-in-a-box, the hydrogen
atom, and multielectron atoms. Well prepared students could quickly read
the first 10 sections of Chapter 1 and begin their serious study with the
Schrodinger wave equation in Section 1-11.O ur presentation of the effects
of electron-electron repulsion in Section 1-14h as been an effective pedagogi
cal tool in discussing the electronic configurations of transition metal atoms.
Chapter 2 begins with a thorough discussion of atomic radii, ionization
potentials, and electron affinities. This is followed by a treatment of Lewis
electron dot structures and the concept of resonance. The latter part of
Chapter 2 introduces molecular geometry through the valence shell electron
pair repulsion approach. Subsequently, molecular symmetry and polarity
are introduced. Section 2-16 provides an insightful method for helping
students to understand and categorize molecular topology.
Chapter 3 is devoted to the valence bond and hybrid orbital descriptions
of chemical bonding. It has been our experience that students often feel
that sp, sp2 and sp3 are the only possible hybridization schemes for s and
,
p orbitals. By introducing the concept of hybridization with the H mole
2
cule, we hope to dispel that notion and provide the student with a straight
forward introduction to the mixing of orbitals.
Chapters 4 and 5 constitute the application of molecular orbital theory to
diatomic and polyatomic molecules,. respectively. Our approach is to tie
the theory of molecular orbitals closely to experimental photoelectron
V
Q
vi Preface
spectroscopy (Section 4-5). The bonding in transition metal diatomic and
triatomic molecules is treated in Sections 4-7, 4-10, and 5-10. In this way
it should be clear that the bonding concepts needed in transition-metal
chemistry are not distinct from those in main-group chemistry. Finally , the
frontier orbital concept and the idea of "allowed " and "forbiddenn reaction s
are discussed in Section 5-9.
The structure and bonding of transition metal complexes is treated in
Chapter 6. A theoretical understanding of the shapes of transition metal
complexes is covered in Section 6-12 by using the angular overlap model
Chapter 7 provides an introduction to bonding in solids and liquids. This
includes a discussion of van der Waals, metallic, and ionic bonding.
In the spring of 197 5 Roger De Kock was teaching an introductory chem
istry course at the American University of Beirut. One of the textbooks
used in this course was Chemical Bonds , written by Harry B. Gray and
published by Benjamin/Cummings in 1973. In the summerof1975 DeKock
wrote a letter to Gray suggesting that the pedagogy of molecular orbital
theory would be enhanced by relating it closely to the experimental tech
nique of photoelectron spectroscopy. Gray responded with enthusiasm and
what resulted was a first draft written during the 1975-76 academic year.
This first draft was revised by DeKock and edited by Jim Hall at the Aspen
Writing Center during the summer of 1976. Gray class-tested the manuscript
for three years (1976-78) and DeKock class-tested it during an interim
course in January, 1979. After each class testing the manuscript underwent
further revision and refinement until it reached its present status. We hope
that this extensive class testing has removed many of the annoyances that
students and instructors often find in first edition textbooks.
We acknowledge the able assistance of Jim Hall during the early stages of
this project. We thank Mary Schwartz of Benjamin/Cummings who acted
as editor and provided constant counsel and encouragement. Dick Palmer
coordinated the production stages and managed to keep us on a tinie
schedule. Thanks also go to Rich Huisman who did several of the initial
drawings and assisted with proofreading and editorial comment. Finally ,
there are numerous individuals who worked at various stages on the typing of
the manuscript, but special thanks go to Jan Woudenberg at Calvin College.
Roger L. DeKock Harry B. Gray
Calvin College Calif omia Institute of Technology
Grand Rapids, Michigan Pasadena, California
February 1980 February 1980
>
Contents
Preface to the Second Edition iii
Preface to the First Edition v
Chapter 1 Atomic Structure 1
1-1 Rutherford's Experiments and a Model for Atomic Structure 1
1-2 Atomic Number and Atomic Mass 2
1-3 Nuclear Structure 3
1-4 Bohr Theory of the Hydrogen Atom 4
1-5 Absorption and Emission Spectra of Atomic Hydrogen 8
1-6 Ionization Energy of Atomic Hydrogen 15
1-7 General Bohr Theory for a One-Electron Atom 17
1-8 Matter Waves 20
1-9 The Uncertainty Principle 21
1-10 Atomic Orbitals 23
1-11 The Wave Equation and the Particle-In-A-Box Problem 24
The Schrodinger Wave Equation 25
The Particle in a Box 26
1-12 The Wave Equation and Quantum Numbers for the
Hydrogen Atom 31
The Quantum Numbers 31
Quantum Number Specifications of Orbitals 34
1-13 Many-Electron Atoms 46
1-14 Effects of Electron-Electron Repulsion in Many-Electron Atoms 51
vi -15 Atomic Energy States and Term Symbols 56
Energy States in Many-Electron Atoms 57
Energy States in Many-Electron Atoms Containing Equivalent
Electrons 59
Ground State Terms for Many-Electron Atoms 62
Determination of Only the Ground-State Tenn Symbol 63
Atomic Energy States and Valence Orbital Ionization Energies 64
Chapter 2 Atomic and Molecular Properties 71
2-1 Lewis Structures for Atoms 71
2-2 Effective Atomic Radii in Molecules 72
2-3 Ionization Energies and Orbital Configurations 7 4
Ionization Energies and Periodicity 78
Ionization Energies of Core Electrons 79
2-4 Electron Affinity 81
2-5 Covalent Bonding 82
2-6 Properties of H and Ht in a Magnetic Field 85
2
2-7 Lewis Structures for Diatomic Molecules 85
vii
viii Contents
2-8 Ionic Bonding 86
2-9 Electronegativity 90
1
2-10 A Covalent Bond with Ionic Character: The HCl Molecule 92
2-11 Lewis Structures for Polyatomic Molecules 93
Methane, Ammonia , and Water 94
Hydrides of Beryllium and Boron 95
Magnesium Chloride, An Ionic Molecule 97
Ammonium Chloride Molecule 97
2-12 Molecules with Double and Triple Bonds 98
2-13 Bonding to Heavier Atoms 101
2-14 Resonance 103
2-15 Molecular Geometry 106
The Valence-shell Electron-pair Repulsion Method and Molecular
Geometry 107
VSEPR Applied to Molecules with Steric Number Greater
than Six 113
E~ceptions to the VSEPR Rules 114
2-16 The Use of Lewis Structures to Predict Molecular Topology 115
2-17 Molecular Symmetry 119
2-18 Polar and N onpolar Polyatomic Molecules 123
Chapter 3 The Valence Bond and Hybrid Orbital Descriptions
of Chemical Bonding 135
3-1 Valence Bond Theory for the Hydrogen Molecule 135
3-2 Valence Bond Theory for the Hydrogen Fluoride Molecule 141
3-3 Valence Bond Theory for the Water Molecule 145
3-4 Valence Bond Theory for the Ammonia Molecule 151
3-5 Valence Bond Theory for Molecules Containing No Lone Pair
Electrons 153
VB Theory for BeH 153
2
VB Theory for BH 155
3
VB Theory for CH 158
4
VB Theory for PH and SH 159
5 6
3-6 Hybrid Orbital Description of Single and Multiple Bonds in Carbon
Compounds 162
Acetylene 166
Benzene 166
3-7 Mathematical Formulation of sp, sp2 and sp3 Hybrid Orbitals 169
,
3-8 Structure and Bonding in the Boranes 173
Chapter 4 The Molecular Orbital Theory of Electronic Structure
and the Spectroscopic Properties of Diatomic
Molecules 183
4-1 Bonding Theory of Ht 184
Molecular-orbital Energy Levels 190
Refinements in the Molecular Orbital Treatment of H;t 194
Contents ix
4-2 Molecular Orbital Theory and Valence Bond Theory for H 195
2
4-3 Net Bonding in Molecules with ls Valence Atomic Orbitals 198
4-4 Molecular Spectroscopy 200
4-5 Photoelectron Spectroscopy: An Experimental Method of Studying
Molecular Orbitals 212
4-6 Molecules withs and p Valence Atomic Orbitals 217
Sigma Orbitals 218
Pi Orbitals 221
s-p Sigma Mixing 223
4-7 Homonuclear Diatomic Molecules 228
Lithium 228
Beryllium 229
Boron 230
Carbon 231
Nitrogen 231
Oxygen 232
Fluorine 232
Neon 233
4-8 Term Symbols for Linear Molecules 233
4-9 The Photoelectron Spectra of N 0 and F 238
2, 2, 2
Oxygen and Fluorine 242
The Photoelectron Spectra of N 0 and F Core Electrons 244
2, 2, 2
4-10 Homonuclear Diatomic Molecules of the Transition Elements 245
The V Molecule 249
2
The Nb Molecule 249
2
The Cu Molecule 250
2
4-11 Heteronuclear Diatomic Molecules 250
Hydrogen Fluoride 250
Carbon Monoxide 256
Boron Monofluoride 256
Bond Properties of other Heteronuclear Diatomic Molecules
and Ions 257
Some Heteronuclear Transition-Metal Molecules 260
Chapter 5 Electronic Structures, Photoelectron Spectroscopy, and
the Frontier Orbital Theory of Reactions of Polyatomic
Molecules 272
5-1 The Simplest Polyatomic Molecule, Ht 272
5-2 Delocalized Molecular Orbitals for BeH and H O 274
2 2
5-3 Delocalized Molecular Orbitals for BH and NH 282
3 3
The Borane Molecule 283
The Ammonia Molecule 288
5-4 Delocalized Molecular Orbitals for CH 292
4
5-5 Photoelectron Spectra for the Isoelectronic Sequence-
Ne, HF, H O, NH and CH 295
2 3, 4
5-6 Delocalized Molecular Orbitals for CO and XeF 297
2 2
Molecular Orbitals for CO 297
2
The Photoelectron Spectrum of CO 302
2
Molecular Orbitals for XeF 303
2
C
X Contents
5-7 Molecular Orbital Theory and Molecular Topology 307
I 5-8 Delocalized Molecular Orbitals in Carbon Compounds 308
Ethylene 308
1:1
i·;
Benzene 312
- 11
5-9 The Frontier-Orbital Concept 315
Proton Affinity and the Frontier-Orbital Concept 316
---. !I The Frontier-Orbital Concept Applied to Reactions of Carbon
Monoxide 321
Symmetry Rules for Chemical Reactions 3 24
Chapter 6 Transition-Metal Complexes 343
6-1 Structures and Stabilities 343
Hard and Soft Metal Ions and Ligands 346
Chelation and Stability 348
6-2 Isomerism 350
Stereoisomerism 350
Constitutional Isomerism 352
6-3 Effective Atomic Number and Stability 353
Effective Atomic Number 353
Metal Carbonyls 355
6-4 Organometallic Complexes 357
'TT
6-5 Coordination Modes of Diatomic Ligands 360
6-6 Metal-Metal Bonds in Re c1s2- and Mo Cl 364
2 6 84+
6-7 Ligand Field Theory for Octahedral Complexes 3 65
Photoelectron Spectroscopy of Octahedral Complexes 373
d-d Transitions and Light Absorption 3 7 6
Factors that Influence the Value of .L\ 377
0
6-8 Ligand Field Theory for Square-Planar Complexes 3 80
6-9 Ligand Field Theory for Tetrahedral Complexes 383
6-10 Charge-Transfer Absorption Bands 385
6-11 Molecular Orbital Theory for Dibenzenechromium 3 87
6-12 The Shapes of Transition-Metal Complexes 391
The Jahn-Teller Theorem 392
The Angular Overlap Model 393
Application of AOM to Four-Coordinate Complexes 397
Application of AOM to Octahedral and Square-Planar
Complexes 403
6-13 Equivalency of the dz2 and d:rs- Orbitals in an Octahedral
JP
Complex 406
6-14 Determining Overlap Integral for d Orbitals in Tetrahedral
Symmetry 408
Chapter 7 Bonding in Solids and Liquids 419
7-1 Elemental Solids and Liquids 419
7-2 Ionic Solids 427