Ion
An atom or group of atoms carrying a net electrical charge because its electron count differs from its proton count.
Unit
C (charge)
In depth
Ions form when atoms gain or lose electrons to reach a more stable configuration, usually a filled valence shell. They are the charge carriers in electrolyte solutions and molten salts, and the electrostatic attraction between oppositely charged ions is what holds ionic solids together.
Examples in the real world
Na⁺ formed by losing one electron, Cl⁻ by gaining one, and the polyatomic sulfate ion SO₄²⁻.