The boiling points of `NH_(3) , H_(2)O` and HF are higher than those of the hydrides of the subsequent members of the group. Give your reasons.

Explanation

Hydrogen is covalently bonded with more electronegative atoms such as F, O and N. The weak electrostatic attractive force is called hydrgen bond.
Because of the association of molecules through hydrogen bonds these hydrides have high boiling points. This is beacuse some extra energy is required to break the hydrogen bond.
The electronegativities of the higher members of `N, O, F` groups are less. So their hydrides are less polar and cannot form hydrogen bonds. Hence the boiling members of the N, O, F group have low boiling points.