Question

Why does NH₃ form hydrogen bond but PH₃ does not?

Answer 1

Nitrogen is more electronegative than the Hydrogen.

Due to this reason, the shared pair of the electrons between H and N are shifted towards the N and N gains the negative charge partially.

On the other hand, H gains the positive charge partially.

Due to the partial positive and negative charge on the H atom and N atom respectively in an ammonia molecule, it forms the inter-molecule hydrogen bond.

Due to very less difference in electro-negativity between P and H there is no intermolecular hydrogen bonding.