2Formation of Ionic Compounds Ionic Compounds—compounds composed of anions and cations.Although they are composed of ions, ionic compounds are electrically neutral.One atom loses electron(s) and achieves a stable noble gas electron configuration; the other atom gains electron(s) and achieves a stable noble gas electron configuration.
3With ionic compounds, there are no single discrete units, only a continuous array of ions. Chemical formula—shows the kinds and numbers of atoms in the smallest representative unit of a substance.The chemical formula of ionic compounds refers to a ratio known as a formula unit (the lowest whole-number ratio of ions).
4Ionic charges are not shown when writing the formula unit of an ionic compound.
5Properties of Ionic Compounds Most are crystalline solids at room temperature.The component ions are arranged in repeating three-dimensional patterns.Large attractive forces between ions result in a very stable structure, so ionic compounds generally have high melting points.
6Coordination number of an ion—the number of ions of opposite charge that surround the ion in a crystal.Ionic compounds can conduct an electric current when melted or dissolved in water.