chemistry help please?

Question

4. As molecular solids, which of the following will exhibit dipole-dipole intermolecular forces: PH3, SO3, Br2, and SiCl4?

a. PH3 only
b. PH3 and SO3
c. SO3 and SiCl4
d. Br2 and SiCl4
e. PH3, SO3, and SiCl4

How can you tell???? and whats the answer

Answer 1

SO3, Br2 and SiCl4 are symmetrical molecules, and will have no dipoles. PH3 is pyramidal, however, and will have (weak) dipole-dipole attractions.