Explanation for exception in a trend? - Chemistry

[hamza2095]

Homework Statement

Homework Equations

The Attempt at a Solution

I have to explain why the boiling point generally increases from groups 14-16 but drops from 16-17, my answer is that every molecule in the the 17th group has only two atoms, meaning there are less protons in the molecule causing a weak london dispersion force. I'm in a relatively low level so I think this answer may do but does anyone have a better explanation or an addition to mine? Any help is appreciated

 

[Borek]

Boiling points increase is observed in all groups, the only exception being molecules from the first period.

Your explanation doesn't touch higher than expected boiling points of ammonia and water.

Hint: ammonia, water and hydrogen fluoride all have sticking out free electron pairs. Do you know any kind of interaction that could utilize them?