Nitrogen exists as diatomic molecule and phosphorus as `P_(4)`. Why?

A diatomic molecules has

Why do halogens exist as diatomic molecules ?

Assertion : In atomic form hydrogen consists of one proton and one electron. Reason : In elemental form hydrogen exists as a diatomic molecule and is called dihydrogen.

White phosphorus (P_4) has

Nitrogen and oxygen exist as diatomic but their congeners are P_(4) and S_(8) respectively because :

Why do they exist as monoatoms in molecules?

Which molecule does not exist ?

Which molecule does not exist ?

Nitrogen forms a simple diatomic molecule but other elements of same group do not form. Explain.

Statement-1 : At room temperature oxygen exists as a diatomic gas, where as sulphur exists as solid. Statement-2 : The catenated -O-O-O- chains are less stable as compared to O=O molecule.