Nitrogen exists as diatomic molecule :
`to` Nitrogen has small size and high electronegativity and nitrogen atom forms `P pi-P pi` multiple bonds with it self (triple bond). So it exists as a discrete diatomic molecule in elementary state.
Phosphorus exists as tetra atomic molecule :
`to` Phosphorus has large size and less electronegative and it forms P-P single bonds. So it exists as tetra atomic i.e., `P_(4)`.
