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 (941.4 kJ mol-1 ). As a result nitrogen is said to be chemically inert in its elemental state. In contrast, P – P single bond is much weaker (213 kJ mol-1 ) than N ☰ N triple bond Therefore, phosphorus is much more reactive than nitrogen.