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# 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.

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