Why does the reactivity of N differ from phosphorus?

Explanation

Nitrogen exists as a diatomic molecule `(NequivN)`. It has a large bond dissociation energy `(941.4 kJcdotmol^(-1))` due to the presence of a triple bond between the two N-atoms. As a result nitrogen is unreactive in its element form.
On the other hand, white or yellow phosphorus exists as a tetraatomk molecule `(P_(4))`. Since the P-P single bond is much weaker `(213kJcdotmol^(-1))` than `NequivN` triple bond `(941.4 kJcdotmol^(-1))` , phosphorus is more reactive than nitrogen.