Ionic compounds are solids, possess high melting points, conduct electricity, are hard but brittle and are formed from an ionic bond between one metal and one nonmetal. An ionic bond is a bond between two elements with opposite charges. The opposing charges attract one another, creating a strong chemical bond.
Ionic compounds dissolve easily in polar solvents, such as water. They do not dissolve readily in nonpolar solvents, which include ether and gasoline. This is because ionic compounds tend to form polar molecules, which dissolve in solutions of similar polarity. A nonpolar solvent does not provide enough energy to break the ionic bond and dissolve the crystalline structure of the compound.
The conductive properties of ionic compounds apply when they are dissolved in an ionic solution or when they are melted. When ionic compounds are solid, they are electrical insulators rather than conductors. This is because electrical charges cannot pass through the tight lattice structure of an ionic compound in its solid state.
Sodium chloride, also known as table salt; potassium chloride, which is used in medicine and as a salt substitute; and corundum, the mineral that rubies and sapphires are composed of, are well-known ionic compounds. All of these compounds form crystal structures, another common trait of ionic compounds.