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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Anion

A negatively charged ion, formed when an atom gains electrons. The added electrons go into the next available orbital in aufbau order, and the anion is larger than its atom.

Ionic solidA regular lattice in which small cations (+) and larger anions (−) alternate, as in sodium chloride. Every ion is held by strong attractions to all its oppositely charged neighbours; there are no separate molecules.+−+−+−−+−+−++−+−+−−+−+−+cations (+) and anions (−) alternate, e.g. Na⁺Cl⁻high melting, brittle; conducts when molten

Example

Sulfur ([Ne] 3s2 3p4[\mathrm{Ne}]\,3s^2\,3p^4) gains two electrons to give sulfide, SX2−\ce{S^2-}, [Ne] 3s2 3p6[\mathrm{Ne}]\,3s^2\,3p^6, the same configuration as argon.

See alsoCationElectron affinityIonic radiusIonic bond