Why does the reactivity of nitrogen differ from phosphorus?
Nitrogen forms pπ−pπ multiple bonds with itself and with other elements having a small size and high electronegativity (such as C and O). Due to this, nitrogen molecule has N≡N triple bond and is non-polar. It has very high dissociation energy (941.4 kJ) and is less reactive under normal conditions. Whereas P is more reactive as it forms P-P single bonds.
