2.5 The hydrogen molecule
Hydrogen, the lightest element, exists as covalently bonded H2 molecules.
However because of its electronic configuration, the octet rule cannot apply.
Why is hydrogen an exception to the octet rule?
Hydrogen has the valence electronic configuration 1s1. There is no 1p orbital.
How can hydrogen acquire a stable outer shell configuration?
The closest noble gas is helium, 1s2, and it can achieve this by sharing its outer electron with another hydrogen atom to form a covalent bond.