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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.