Valence

Valence, ability of an atom to form compounds, expressed as the number of electrons an element gives up or accepts from other elements. The meaning of the term has undergone several changes over the past century. One of the first definitions of valence referred to the number of hydrogen atoms with which an atom of a different element could combine. The term then came to encompass the bonding capabilities of ionized (electrically charged) atoms.

See also: Bond, chemical.