Chem 20 AP
Formal Charges and Resonance Structures
1. (a) Write a Lewis structure for PF3.
(b) Determine the formal charge of the P and F atoms.
2. Write Lewis structures that obey the octet rule for each of the following, and assign formal
charges to each atom:
(a) NO+
(b) POCl3 (P is bonded to the three Cl atoms and to the O)
(c) ClO4
(d) HClO3 (H is bonded to O)
3. For each of the following molecules or ions of sulfur and oxygen, write a single Lewis
structure that obeys the octet rule, and calculate the formal charges on all the atoms:
(a) SO2
(b) SO3
(c) SO32
(d) Arrange these molecules/ions in order of increasing S – O bond distance
4. Consider the nitryl cation, NO2+.
(a) Write one or more appropriate Lewis structures for this ion.
(b) Are resonance structures needed to describe the structure?
(c) With what familiar molecule is it isoelectronic?