Question

Why is NH3 more basic than PH3?

Answer 1

Basically NH₃ is a base due to the lone pair of electrons present on the Nitrogen atom which is available for donation. On the other hand PH₃ is also a base but its basic character is less than that of NH₃ because the nitrogen in phosphorous have lone pair of electrons that are not readily available for donation.

Also the P-H bonds are weaker than N-H bonds, so there’s not as much compensation for protonating PH₃. This is a result of the inert pair effect, seen in heavier elements.

Answer 2

es NH3 is more basic than PH3 as NH3 has more density of electron. Owing it to the small size of nitrogen and small P orbitals it has the ability to form stronger bonds due to effective overlap. In PH3 however, the large size of P results in the P orbitals becoming diffused preventing effective overlap.