As indicated in the previous section, all ionic compounds are comprised of a definite ratio of cations and anions. This ratio of ions within the ionic compound is determined by the oxidation state of the cation and anion. In every ionic compound, the total positive charge of the cations must always equal the total negative charge of the anions, so that the net charge of the complex is always zero. Every ionic compound can be described by an ionic formula unit which lists the simplest whole number ratio of the ions in the ionic crystal lattice formed. The simplest whole number ratio of the sodium and chloride ions the network of ions shown above is:

Hence, the chemical formula for the ionic compound sodium chloride, " NaCl ". See exercise 3