An ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions. Ionic compounds usually form when a metal reacts with a nonmetal, where the metallic atoms lose an electron or electrons, becoming cations, and the nonmetallic atoms gain an electron or electrons, becoming anions. Once the ions form, if they are in close proximity, their opposite charges attract, forming an ionic compound. Ionic compounds can also form when metals and polyatomic ions interact.

Some key properties of ionic compounds include:

• High melting and boiling points: Ionic bonds are very strong, and a lot of energy is required to break them.
• Brittleness: Ionic compounds are strong but brittle, meaning they can easily break or shatter when subjected to stress.
• Solubility: Ionic compounds are often soluble in water and other polar solvents.

Ionic compounds have a wide variety of uses and applications. Many minerals are ionic, and humans have processed common salt (sodium chloride) for over 8000 years, using it first as a food seasoning and preservative, and now also in manufacturing, agriculture, water conditioning, for de-icing roads, and many other uses. Ionic compounds are also used as precursors for high-temperature solid-state synthesis, and many metals are geologically most abundant as ionic compounds within ores.