noun one of the elements which appear at the respective poles when a body is subjected to electro-chemical decomposition. ·cf. anion, cation.
2. ion ·add. ·noun one of the electrified particles into which, according to the electrolytic dissociation theory, the molecules of electrolytes are divided by water and other solvents. an ion consists of one or more atoms and carries a unit charge of electricity, 3.4 x 10-10 electrostatic units, or a multiple of this. those which are positively electrified (hydrogen and the metals) are called cations; negative ions (hydroxyl and acidic atoms or groups) are called anions.
3. ion ·add. ·noun one of the small electrified particles into which the molecules of a gas are broken up under the action of the electric current, of ultraviolet and certain other rays, and of high temperatures. to the properties and behavior of ions the phenomena of the electric discharge through rarefied gases and many other important effects are ascribed. at low pressures the negative ions appear to be electrons; the positive ions, atoms minus an electron. at ordinary pressures each ion seems to include also a number of attached molecules. ions may be formed in a gas in various ways.