2 Formation 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.
3 With 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).
4 Ionic charges are not shown when writing the formula unit of an ionic compound.
5 Properties 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.
6 Coordination 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.