Chapter 8, Problem 8.79SP

Which of the following substances would you expect to have a nonzero dipole moment? Explain, and show the direction of each.
(a) ${\text{NF}}_{\text{3}}$  (b) ${\text{CH}}_{\text{3}}{\text{NH}}_{\text{2}}$
(c) ${\text{XeF}}_{\text{2}}$  (d) ${\text{PCl}}_{\text{5}}$