what is anion

An anion is an ion with a negative charge, meaning it has more electrons than protons. Anions are formed when an atom gains one or more electrons, typically pulled away from other atoms with a weaker affinity for them. The number of electrons gained, and so the charge of the ion, is indicated after the chemical symbol, for example, chlorine (Cl) gains one electron to become Cl-, whilst oxygen (O) gains two electrons to become O2- . Anions are a type of atom, the smallest particle of an element that still retains the elements properties.