Sodium bromide, potassium bromide, sodium chloride, sodium fluoride, potassium iodide, potassium chloride, calcium chloride, potassium oxide and magnesium oxide are all compounds with ionic bonds. Ionic compounds consist of a metal bonded to a nonmetal.
Ionic bonds result from the transfer of electrons from a metal to a nonmetal. Metals tend to lose electrons, as they have only a few in the outer layer. Nonmetals, which only need one or two electrons to fill the outer layer, have a tendancy to gain electrons. Electron affinity, the energy given off when an atom gains electrons, is balanced with the energy required to move an electron from a neutral atom, known as the ionization potential, to form a stable ionic compound.
Compounds that contain ionic bonds are generally solids with high melting and boiling points that conduct electricity when melted or dissolved. They generally serve as insulators in a solid state, and are very hard and brittle. Ionic compounds form crystalline structures, an arrangement that minimizes repulsions and maximizes attractions around each ion. When crushed, ions of like charge are pushed together, and the electrostatic repulsion splits the crystal apart. Ionic compounds dissolve more readily in water or other polar solvents and tend not to dissolve in nonpolar solvents, such as gasoline.