Ionic bonds have high boiling and melting points. A lot of energy is needed to overcome the attraction between the negative and positive ions in ionic compounds.
Ionic solids are insulators. Since ions in ionic solids are tightly bound, they cannot conduct electricity. However, when the solid is dissolved in water, the separated ions can freely move and conduct electricity through the solution. The strong attraction between negative and positive ions also causes ionic solids to harden.
An ionic bond is formed when a non-metal reacts with a metal. Common examples of ionic compounds include sodium chloride (NaCl) and magnesium oxide (MgO).