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Chapters 10 and 11 Outline Chapter 10: The Shape of Molecules and Chapter 11: Theories of Covalent Bonding In Chap. 10, the text covers the use of a classical approach, called Valence Shell Electron Pair Repulsion (VSEPR) Theory to predict the shapes of molecules with coordination numbers of 2 - 6. In Chap. 11, the text introduces the use of Quantum Mechanics (Valence Bond Theory and Orbital Hybridization) to characterize molecular structure. In most textbooks, these two topics are covered in the same chapter, and that I prefer this approach. For a given coordination number, we will first show how the structure can be predicted by VSEPR and then show how it is characterized using Quantum Mechanics. Text Problems: Chapter 10: #54, 61(XeF2 and XeF4) , 66, 79, 81 Chapter 11: #2, 10, 35, 37 + Supplementary Questions (attached) Text Sample Problems: The text has a number of excellent sample problems (solved in detail) in each section. I would recommend that you study these problems + the "follow up" problems, which have brief solutions at the end of the chapter. Chapter 10: The Shape of Molecules Sect. Title and Comments Required? 1. Depicting Molecules and Ions with Lewis Structures We included this material in the last Chapter 2. Valence-Shell Electron-Pair Repulsion (VSEPR) Theory and Molecular Shape YES Molecular Shape and Molecular Polarity YES 3. ALREADY COVERED Chapter 11: Theories of Covalent Bonding Sect. Title and Comments Required? 1. Valence Bond (VB) Theory and Orbital Hybridization YES 2. Modes of Orbital Overlap and Types of Covalent Bonds YES 3. Molecular Orbital (MO) Theory and Electron Delocalization YES Chapters 10 & 11 Supplementary Homework Questions Part 1: General 1. Which of the following molecules is/are polar? CCl4, SF4, CS2, NF3, PF5? (A) CS2 and PF5 (D) SF4 only 2. (B) CS2 and SF4 (E) SF4 and NF3 Draw the Lewis Structures of the three isomers of dichloroethene and determine whether each molecule is polar or non-polar. (a) 1,1-dichloroethene 3. (b) trans-1,2-dichloroethene (c) cis-1,2-dichloroethene What is the hybridization of the nitrogen atom in the following molecules? (a) CH3NO2 4. (C) NF3 only (F) PF5 only (b) :N(CH3)3 (c) NO+ (d) CH3CN Which of the following shapes is not possible for a molecule in which the central atom has sp3d hybridization? (A) linear (B) trigonal bipyramidal (C) tetrahedral (D) T-Shaped (E) seesaw 5. SiF62- exists, but CF62- does not. Why? Use the concept of hybrid orbitals in your answer. (A) (B) (C) (D) (E) Silicon is less electronegative, so its hybrid orbitals are lower in energy Carbon is never found in 2- ions Silicon is unusual, and hybridization is irrelevant Carbon sp3 cannot accommodate six ligands Silicon can hybridize using d orbitals not available in carbon. 6. Predict the order of the N-O bond lengths (lowest to highest) in NO+ , NO2-, NO3- . 7. Predict the order of the N-O bond enthalpies (lowest to highest) in NO+ , NO2-, NO3- . 8. Predict the order of the N-O vibrational stretching frequencies (lowest to highest) in NO+ , NO2-, NO3- . MO Theory 9. Draw the valence shell electron configuration of the following diatomic molecules or molecular ions, indicate the bond order, and whether the molecule is diamagnetic or paramagnetic. (a) B2 10. (c) N2 (d) NF (e) O22- Indicate which of the following diatomic molecules or molecular ions can exist. (a) HeH 11. (b) BN (b) F22- (c) Ne2+ Rank the following 3 species in order of (a) increasing bond length, (b) decreasing vibrational frequency, (c) increasing bond enthalpy: NF, NF+, NF- Answers to the Supplementary Homework Questions are posted on the course web site. Questions about these Problems will be answered in Recitation. Supplementary Homework Questions Part 2: VSEPR/Hybridization For each of the molecules and ions below, determine the following quantities: (a) (b) (c) (d) (e) (f) NBA = Number of Bonded Atoms NLP = Number of Lone Pairs of Electrons SN = Steric Number (=NBA+NLP) HY = Hybridization EPG = Electron Domain Geometry MG = Molecular Geometry 1. AsF3 2. NO3- 3. SF2 4. ICl4- 5. SO32- 6. NO2- 7. IF5 8. GeCl4 9. SeF5- 10. TeBr4 11. BrCl3 12. CO3213. XeF2 14. SeCl4215. PF4+ 16. ClF217. AsF5 Answers to the Supplementary Homework Questions are posted on the course web site. Questions about these Problems will be answered in Recitation.