The number of valence electrons determines the valence of an atom. The number of free valence electrons or valence places corresponds to the valence of an atom. An atom with one valence electron is monovalent and can have only one single bond with another atoms. Bivalent atoms already have the choice to form a double bond with another bivalent atom or to form two single bonds, depending on the respectively available binding partners. An atom can be quadrivalent at most.