Question

Why does NH₃ form hydrogen bond but PH₃ does not?

Answer 1

The electronegativity of N (3.0) is much higher than that of FI (2.1). As a result, N – H bond is quite polar and hence NH₃ undergoes intermolecular H-bonding. In contrast, both P and H have an electronegativity of 2.1. Therefore P – H bond is non-polar and hence PH₃ does not undergo H – bonding.