Why does Nitrogen show anomalous behaviour in its group ?

Explanation

Nitrogen, the first member of Group 15 elements, differ from other elements of the group due to the following reasions :
(i) It has very small size.
(ii) It has high electronegativity
(iii) It has high ionisation enthalpy.
(iv) It does not have d-orbitals in its valence shell.
(v) It forms multiple bonds easily.
Differences of nitrogen from other family members (Anomalous behaviour).
(i) Nitrogen is a gas while other elements are solids
(ii) Nitrogen can from hydrogen bonds while other elements of this group cannot do so.
(iii) Nitrogen does not form pentahalides while other elements form pentahalides.
(iv) Nitrogen exists as `N_2` while other family members cannot form stable diatomic molecules.