ion

/ˈaɪɑn/

/ˈaɪən/

Other forms: ions

An ion is an atom or particle with a positive or negative electrical charge. Think of an ion as having a plus or minus sign.

Ion is a word you are most likely to encounter in a physics or chemistry text. But you don’t have to be a chemist or physicist to understand the concept. If you had a neutral particle and you were able to remove or add an electron, then you would have an ion — a charged particle. Don't confuse the tiny ion with the similar word eon, which is an extremely long period of time.

Definitions of ion

1. noun

   a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons
   types:

   anion

   a negatively charged ion

   cation

   a positively charged ion

   hydrogen ion

   a positively charged atom of hydrogen; that is to say, a normal hydrogen atomic nucleus

   diazonium

   the univalent cation R-N:N- (where R is an aromatic hydrocarbon); found in salts that are used in manufacturing azo dyes

   hydroxide ion, hydroxyl ion

   the anion OH having one oxygen and one hydrogen atom

   superoxide, superoxide anion

   the univalent anion O2-

   type of:

   particle, subatomic particle

   a body having finite mass and internal structure but negligible dimensions