Valence is a measure of the combining power of a particular element. Valence (also called valency) is equal to the number of individual chemical bonds that one atom can form. The valence of an atom is determined by the number of electrons in the outermost (valence) shell (see valence electron). The valence of many elements is determined by their ability to combine with hydrogen or displace it in compounds (hydrogen has a valence of 1). For example, one carbon atom combines with four hydrogen atoms to make methane so the valence of carbon is given as 4. In general, the characteristic valence of an element in Group N of the periodic table is N or (8 - N).