valence combining capacity of an atom expressed as the number of single bonds the atom can form or the number of electrons an element gives up or accepts when reacting to form a compound. Atoms are called monovalent, divalent, trivalent, or tetravalent, according to whether they form one, two, three, or four bonds (see chemical bond ). The Relationship of Electrons and Valence For purposes of describing chemical behavior, an atom can be considered as a positively charged nucleus surrounded by negatively charged electrons orbiting in concentric spherical shells. The number of positive... Read more