Ionic compounds consist of cations and anions. Cations are positively charged ions. Anions are negatively charged ions. The name of an ionic compound is based on the names of the component ions. A roman numeral in parenthesis is used for elements that can form more than one positive ion. It is also common to see the endings -ous or -ic to indicate the ionic charge of cations.

These endings are added to the Latin name of the element to represent the ions with lesser or greater charge. The -ide ending is added to the name of a monatomic ion of an element. Polyatomic anions that contain oxygen are called oxyanions. When an element forms two oxyanions, the one with less oxygen is given a name ending in -ite and the one with more oxygen is given a name that ends in -ate. When there is a series of four oxyanions, the prefixes hypo- and per- are used along with the endings -ite and -ate.