Question

Would you expect the hydrides of $N,O$ and $F$ to have lower boiling points than the hydrides of their subsequent group members ? Give reasons.

Answer 1

On the basis of molecular masses of $N{H}_3,H_{2}O$ and $HF,$ their boiling points are expected to be lower than those of the subsequent group member hydrides.

However, due to higher electronegativity of $N,O$ and$F,$ the magnitude of hydrogen bonding in their hydrides will be quite appreciable. Hence, the boiling points $N{H}_3,H_{2}O$ and $HF$ will be higher than the hydrides of their subsequent group members.