Anion
A negatively charged ion produced when an atom or molecule gains one or more electrons.
Formula / equation
X + n e⁻ → Xⁿ⁻
Unit
C (charge)
In depth
Anions are larger than their parent atoms because the added electrons increase mutual repulsion while the nuclear charge stays fixed. Non-metals with high electron affinities form anions readily. During electrolysis anions travel to the positively charged anode.
Examples in the real world
Cl⁻, O²⁻, S²⁻, and the polyatomic nitrate NO₃⁻ and carbonate CO₃²⁻ ions.