Properties of Ionic/Covalent Compounds and Metals

Ionic Compounds

Ionic compounds typically have high melting and boiling points, and are hard and brittle. As solids they are almost always electrically insulating, but when melted or dissolved they become highly conductive, because the ions are mobilized.

Solubility is highest in polar solvents (such as water) or ionic liquids, but tends to be low in nonpolar solvents (such as petrol/gasoline).

Covalent Compounds

Covalent compounds fall in to two types; simple molecules and giant covalent structures. Simpler molecular substances have low melting and boiling points and are non-conductive. Giant covalent structures have very high melting points and, with the exception of graphite, non-conductive.

Simpler molecule substances are often soluble in non-polar solvents while the covalent bonds are so strong they are insoluble in polar and non-polar solvents.

Metals

Metals have giant structures held together by strong electrostatic attractions between positive ions and negative electrons which cause them to have high melting and boiling points. They are good conductors of heat and electricity.