CH 221 – Ziegler KEY CONCEPTS Chapter 8 & 9
Fall 06 10th Ed.
Class period 1 -- Reading pp. 300- 304; 306 (b) – 307 (m); 312- 313.
1. State the number of valence electrons for a main-group element. Problems 8.1, 8.7
2. Draw the electron-dot symbol for a main-group element. Problems 8.11, 8.17
3. State the “octet rule.” Problem 8.8
4. Identify periodic trends in electronegativity. Problem 8.37
Class period 2 -- Reading pp. 313 – 324; 344 – 353
5. Predict the polarity of a bond. Problem 8.39, 8.40
6. Draw Lewis structures for molecules and polyatomic ions. Problems 8.45, 8.46.
7. Use calculated Formal Charges to evaluate Lewis structures. Problem 8.47, 8.50
8. Write resonance forms. Problems 8.51, draw the resonance forms for 8.50 a & b
9. Use the Lewis structure to predict molecular geometry and bond angles. (Note: you will
be required to do this only for molecules and ions in which the octet rule is satisfied for all
atoms.) Problems 9.21 a-d., 9.25, 9.26
Class period 3 -- Reading pp. 357 – 358; 360 – 365(t); 365 (m) – 369
10. From the geometry of a polyatomic ion or molecule, predict whether it is polar or
nonpolar. Problems 9.32, 9.35, 9.37.
11. State the hybridization in a covalently bonded species. Problem 9.54 a.
12. State the number of pi and sigma bonds in a molecule or polyatomic ion. Problem 9.54 b-
e; and for the molecules in Problems 9.25, and 9.26, state the number of sigma and pi
bonds in each molecule.
Answers to Problems not in the appendix:
8.1 a) Group IV (AKA 14) b) Group II (AKA 2) c) Group V (AKA 15)
8.8 a) The “octet rule” is the observation that atoms will gain lose or share electrons to achieve the
stable configuration (full shell like the noble gases) of 8 valence electrons. The reason it is in quote
marks is that it has so many exceptions, specifically, H, He, (which have a full shell of 2) and pretty
much everything in the lower periods can have more than 8.
b) S needs 2 more electrons. c) This configuration needs only 3 more electrons.
8.40 a) O-F < C-F < Be-F b) C-P< S-Br < O-Cl c) C-S < N-O < B-F
8.46 a) H2CO
H
C
H
O
b) H2O2
OO
H
H
c) C2F6
C C
F
F
F
F
F
F
d) AsO33-
As
O
O
O
