Ion

An atom or group of atoms that have either gained or lost electrons and therefore have an unbalanced charge. This charge will cause them to be attracted or repelled from other charged particles or objects.

Positively-charged ions are called cations; negatively charged ions are called anions. Ions will have different properties than the atoms from which they are made.

Example: Chlorine atoms form a diatomic (two atomed) molecule Cl₂ which is a green poisonous gas. The ion formed by a chlorine atom when it gains an electron is the chloride ion Cl^-. When this ion combines with a sodium ion Na⁺ they form common table salt.

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