Ionic compounds are composed of ions in a hard yet brittle crystalline solid form. They have high melting and boiling points and they conduct electricity when melted to liquid-form. Most are soluble in water. Most ionic compounds, however, are not soluble in non-polar solvents such as diethyl ether or gasoline.
Ionic compounds are often contrasted with covalent compounds due to their differing properties. Covalent compounds are solids, liquids or gases composed of covalently bound molecules. Covalent solids generally have low melting points, and covalent liquids have low boiling points, according to a hyperphysics page on the Georgia State University website. In all phases, covalent compounds are poor electrical conductors. Most covalent compounds are not soluble in water, but are soluble in non-polar solvents.