General Chemistry Principles and Modern Applications Petrucci Harwood Herring 8 th Edition Chapter 12: Chemical Bonding II: Additional Aspects Philip Dutton University of Windsor, Canada N9B 3P4 Prentice-Hall 2002
Contents 12-1 What a Bonding Theory Should Do 12-2 Introduction to the Valence-Bond Method 12-3 Hybridization of Atomic Orbitals 12-4 Multiple Covalent Bonds 12-5 Molecular Orbital Theory 12-6 Delocalized Electrons: Bonding in the Benzene Molecule 12-7 Bonding in Metals Focus on Photoelectron Spectroscopy Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 2 of 47
12-1 What a Bonding Theory Should Do Bring atoms together from a distance. e - are attracted to both nuclei. e - are repelled by each other. Nuclei are repelled by each other. Plot the total potential energy verses distance. -ve energies correspond to net attractive forces. +ve energies correspond to net repulsive forces. Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 3 of 47
Potential Energy Diagram Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 4 of 47
12-2 Introduction to the Valence-Bond Method Atomic orbital overlap describes covalent bonding. Area of overlap of orbitals is in phase. A localized model of bonding. Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 5 of 47
Bonding in H 2 S Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 6 of 47
Example 12-1 Using the Valence-Bond Method to Describe a Molecular Structure. Describe the phosphine molecule, PH 3, by the valence-bond method.. Identify valence electrons: Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 7 of 47
Example 12-1 Sketch the orbitals: Overlap the orbitals: Describe the shape: Trigonal pyramidal Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 8 of 47
12-3 Hybridization of Atomic Orbitals Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 9 of 47
sp 3 Hybridization Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 10 of 47
sp 3 Hybridization Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 11 of 47
Bonding in Methane Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 12 of 47
sp 3 Hybridization in Nitrogen Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 13 of 47
Bonding in Nitrogen Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 14 of 47
sp 2 Hybridization Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 15 of 47
Orbitals in Boron Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 16 of 47
sp Hybridization Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 17 of 47
Orbitals in Beryllium Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 18 of 47
sp 3 d and sp 3 d 2 Hybridization Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 19 of 47
Hybrid Orbitals and VSEPR Write a plausible Lewis structure. Use VSEPR to predict electron geometry. Select the appropriate hybridization. Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 20 of 47
12-4 Multiple Covalent Bonds Ethylene has a double bond in its Lewis structure. VSEPR says trigonal planar at carbon. Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 21 of 47
Ethylene Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 22 of 47
Acetylene Acetylene, C 2 H 2, has a triple bond. VSEPR says linear at carbon. Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 23 of 47
12-5 Molecular Orbital Theory Atomic orbitals are isolated on atoms. Molecular orbitals span two or more atoms. LCAO Linear combination of atomic orbitals.? 1 = f 1 + f 2? 2 = f 1 - f 2 Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 24 of 47
Combining Atomic Orbitals Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 25 of 47
Molecular Orbitals of Hydrogen Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 26 of 47
Basic Ideas Concerning MOs Number of MOs = Number of AOs. Bonding and antibonding MOs formed from AOs. e - fill the lowest energy MO first. Pauli exclusion principle is followed. Hund s rule is followed Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 27 of 47
Bond Order Stable species have more electrons in bonding orbitals than antibonding. Bond Order = No. e- in bonding MOs - No. e- in antibonding MOs 2 Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 28 of 47
Diatomic Molecules of the First-Period BO = (e - bond - e- antibond )/2 BO = (1-0)/2 = ½ H 2 + BO = (2-0)/2 = 1 H 2 + BO He 2 + = (2-1)/2 = ½ BO = (2-2)/2 = 0 He 2 + Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 29 of 47
Molecular Orbitals of the Second Period First period use only 1s orbitals. Second period have 2s and 2p orbitals available. p orbital overlap: End-on overlap is best sigma bond (s ). Side-on overlap is good pi bond (p). Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 30 of 47
Molecular Orbitals of the Second Period Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 31 of 47
Combining p orbitals Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 32 of 47
Expected MO Diagram of C 2 Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 33 of 47
Modified MO Diagram of C 2 Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 34 of 47
MO Diagrams of 2 nd Period Diatomics Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 35 of 47
MO Diagrams of Heteronuclear Diatomics Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 36 of 47
12-6 Delocalized Electrons Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 37 of 47
Benzene Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 38 of 47
Benzene Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 39 of 47
Ozone Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 40 of 47
12-7 Bonding in Metals Electron sea model Nuclei in a sea of e -. Metallic lustre. Malleability. Force applied Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 41 of 47
Bonding in Metals Band theory. Extension of MO theory. N atoms give N orbitals that are closely spaced in energy. N/2 are filled. The valence band. N/2 are empty. The conduction band. Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 42 of 47
Band Theory Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 43 of 47
Semiconductors Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 44 of 47
Photovoltaic Cells Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 45 of 47
Focus on Photoelectron Spectroscopy Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 46 of 47
Chapter 12 Questions 1, 3, 8, 10, 16, 29, 33, 39, 45, 59, 68, 72, 76 Prentice-Hall 2002 General Chemistry: Chapter 12 Slide 47 of 47