Why does hydrogen occur in a diatomic from rather than in a monoatomic form under normal conditions?

Explanation

Hydrogen atom has only one electron in its valence shell `(1s^(1))` and has only one electron less than the stable noble gas configuration of helium. Therefore, it shares its single electron with electron of other H-atom to achieve stable inert gas configuration of He. Therefore, it readily forms diatomic molecule and exists as `H_(2)` rather than monoatomic.