Last modified on May 22, 2015, at 17:51
An electrostatic potential map of the nitrate ion (NO3). Areas colored red are lower in energy than areas colored yellow

An ion is an atom or molecule that possesses a number of electrons that is greater or lower than the number of protons, yielding a net electric charge.[1]

An ion with a positive ( + ) charge is called a cation. An ion with a negative ( - ) charge is called an anion. An ion with both a positive and negative charge is a zwitterion.


  1. Wile, Dr. Jay L. Exploring Creation With Chemistry. Apologia Educational Ministries, Inc. 1998