An anion (pronounced with 3 syllables, as in "an eye on") is a negatively charged ion. It is the opposite of a cation and will react with one to form an ionic compound. It is so named because, during electrolysis, it migrates toward the anode. Anions consist of electronegativity nonmetals, especially oxygen, sulfur, and the halogens, that have gained additional electrons by chemical reaction, often in combination with other elements. The further to the right side of the periodic table an element is, the greater the chance that it will form an anion. In a sodium chloride solution the Na+ ions are cations and the Cl- ions are anions.
- Wile, Dr. Jay L. Exploring Creation With Chemistry. Apologia Educational Ministries, Inc. 1998