When comparing molecules, how can i judge which would have a higher boiling point?

Question

For example comparing ICl to Br_2_
or...
PH_3_ to SiH_4_
Only with the help of a periodic table.

Answer 1

The boiling point is related to the attraction of intermolecular forces.

The more attraction, due to polarity or ionic bonding, then the higher the BP. When the bonding is equal, the higher molecular mass will have the higher BP.

Answer 2

Boiling point refers to a compound's ability to over come their inter-molecular attractions and escape due to adding energy. Covalent bonds are relatively strong and polar bonds have unequal electronegativity levels such as H2O. The more stuff there is means more mass which means a higher boiling point. Hope this makes sense. :)