Illustrated Glossary of Organic Chemistry

Valence electron: An electron in an atom's valence shell; a lone pair electron or an electron which is part of a covalent bond.

Electron Configuration for Atomic Carbon

Atomic carbon has six electrons: two inner shell (core) electrons in the 1s orbital, and four valence (outer most shell) electrons in the 2s and 2p orbitals.

Electron Configuration for Bonded Carbon

When bonded with a full octet (such as in methane) carbon has eight valence electrons (two per covalent bond). Each hydrogen atom has two valence electrons.