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Chemistry vocabulary · Atoms and the Periodic Table

Anion

Meaning in chemistry, with examples

/ˈænaɪən/nounCommon term

In chemistry, anion means: An ion with a negative charge, formed when an atom or group of atoms gains electrons. Cl⁻, OH⁻ and SO₄²⁻ are examples.

In Turkish: anyon

How it is used

Used together with 'cation'. Nonmetals usually form anions, whose names often end in '-ide' (chloride, oxide), or in '-ate' and '-ite' when they contain oxygen (sulfate, nitrite). In electrolysis anions move toward the anode.

Example sentences

  1. Silver nitrate is used to test for halide anions such as chloride.

  2. Sulfate is a polyatomic anion with a 2− charge.

Common collocations

  • polyatomic anion
  • halide anion
  • anion exchange
  • form an anion
  • cationAn ion with a positive charge, formed when an atom or group of atoms loses electrons. Na⁺, Ca²⁺ and NH₄⁺ are examples.
  • ionAn atom or group of atoms that carries an electric charge because it has gained or lost electrons. Positive ones are cations and negative ones are anions.
  • ionic bondThe strong attraction between positive and negative ions that forms when one atom, usually a metal, transfers electrons to another, usually a nonmetal. Sodium chloride is the classic case.
  • saltAn ionic compound made of positive and negative ions, usually formed when an acid reacts with a base. Sodium chloride is the best known, but there are thousands of others.
  • electronA tiny particle with a negative charge that moves around the nucleus of an atom. Chemical bonds and reactions are mostly about how these particles are shared or transferred.

More terms: Atoms and the Periodic Table

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