Orthophosphoric acid ($H_3PO_4$) is a tribasic acid.

Hypophosphorous acid ($H_3PO_2$) is a tribasic acid.

Pyrophosphoric acid ($H_4P_2O_7$) is a tetrabasic acid.

Phosphorous acid ($H_3PO_3$) is a dibasic acid.

Single $N - N$ bond is weaker than single $P - P$ bond

${N_2}{O_4}$ has two resonance structures

The stability of hydrides increases from $N{H_3}{\rm{ to }}Bi{H_3}$ in Group 15

Nitrogen cannot form $d\pi - p\pi$ bonds $