Since every atom contains equal numbers of positive and negative charges, the oxidation state or oxidation number of any atom is always zero. This is illustrated by simply totaling the opposite charges of the atoms as shown by the following examples. The transfer of electrons between the atoms of these elements results in drastic changes to the elements involved. This is due to the formation of ionic compounds . The reaction between sodium and chlorine serves as a typical example.
Chlorine is greenish colored gas.
Sodium chloride exhibits properties quite distinct and different from sodium and chlorine. The changes in physical as well as chemical properties are due to the formation of cations and anions via the oxidation-reduction process, and the resultant, powerful attractive force that develops between these oppositely charge ions . This force of attraction is called the ionic, electrostatic or electrovalent bond , and serves to keep the sodium and chloride ions tightly bound in a highly organized network or lattice of alternating positive and negative charges. This entire complex of ions is called an ionic compound, and is illustrated below in two dimensions. Note how the oppositely charged ions are arranged.