VALENCE ELECTRON

Electrons that can be actively involved in chemical change; usually electrons in the shell with the highest value of n. For example, sodium's ground state electron configuration is 1s 2 2s 2 2p 6 3s 1 ; the 3s electron is the only valence electron in the atom. Germanium (Ge) has the ground state electron configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 2 ; the 4s and 4p electrons are the valence electrons.