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Chapter 9 Study Guide
Chapter 9 presents a working theory of chemical bonding that,
while largely qualitative and somewhat rough in places, nevertheless
does an excellent job of explaining the existence of
nearly all commonly observed molecules and ionic crystals.
The ionic and covalent bonding cases are introduced separately
and then unified through the idea of polar covalent bonds and
electronegativities. The correspondence between multiple bonds
and bond lengths is discussed, as well as bond dipoles,
resonance structures, etc. Throughout, Lewis dot structures
and symbols are used.
Some of this material was covered by Professor Allen; her
transparencies are downloadable as
PDF files here and here.
Suggested Problems
The following problems (in the textbook) are illustrative of the
important concepts covered in this chapter, and are of comparable
(or greater!) difficulty with what you might see on homeworks or exams:
Chapter 9, problems 29, 30, 33-38, 39, 41, 42, 43, 44, 47, 48, 49,
55, 56, 57, 58, 65, 67, 69, 71, 72, 75, 76, 79, 83, 84.
You should be able to:
- Explain why chemical bonds form as a result of electrostatic
(charge-charge) interactions between electrons and nuclei.
- Explain what lattice energy is.
- Apply the Born-Haber cycle to the formation of ionic crystals.
- Draw Lewis structures for atoms, ions, and small molecules.
- Calculate formal charges.
- Identify the polarity of bonds based on electronegativities.
- Identify the Periodic trends in electronegativity.
Important topics and Concepts
- Electrostatic interactions are the ultimate source of bonding
in both covalent molecules and ionic crystals!
- Lewis theory
- Valence electrons are the important ones
- The noble-gas configuration is especially stable
- Electrons can be either transferred or shared
- Ionic crystals
- Lattice energy as a stabilizing force
- The Born-Haber Cycle
- Conventions for the sign of the lattice energy
- Covalent bonds
- Electrons share in pairs
- Single, double, and triple bonds
- Polarity
- Electronegativity
- How to draw Lewis structures
- Formal charges
- Resonance between multiple rational Lewis structures
- Exceptions
- Correlations of bond length, bond energy, and bond order
- Bonding in hydrocarbons
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