Why does the reactivity of nitrogen differ from phosphorus?

Explanation

Nitrogen exists as a diatomic molecule (N = N). Due to the presence of a triple bond between the two N-atoms, the bond dissociation energy is large. As a result, nitrogen is inert and unreactive in its elemental state.
In contrast, white or yellow phosphorus exists as a temperature molecule `(P_4)`. Since the P-P single bonds is much weaker than `N -= N` triple bond, therefore, phosphorus is much more reactive than nitrogen. Another factor for the large reactivity of phosphorus is the presence of angular strain in its molecule. Presence of angular strain in phosphorus makes it highly reactive.