Question

Proton affinities of NH3 and PH3

Answer 1

nh3 anx ph3 or ch2 ay be

Answer 2

The size of N atom is less than the size of P atom. So the electron density on N atom is more than that on P atom.Hence it becomes a stronger base i.e. it extracts H+ easily which make it have a higher proton affinity than PH3.
OR
The nitrogen atom(N) in ammonia NH3 more electronegative then the phosphorus atom(P) in phosphine PH3. Thus NH3 has more proton affinity than PH3.