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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Cation

A positively charged ion, formed when an atom loses electrons. Electrons leave from the highest nn first (for transition metals, all nsns before any (n−1)d(n-1)d), so a cation is smaller 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

Ca\ce{Ca} ([Ar] 4s2[\mathrm{Ar}]\,4s^2) loses two electrons to give CaX2+\ce{Ca^2+}, [Ar][\mathrm{Ar}]. Mn\ce{Mn} ([Ar] 4s2 3d5[\mathrm{Ar}]\,4s^2\,3d^5) gives MnX2+\ce{Mn^2+}, [Ar] 3d5[\mathrm{Ar}]\,3d^5.

See alsoAnionIonic radiusIonization energyIonic bond