What is an ionic crystal?

An ionic crystal is one in which ionic bonds form the structure, or lattice, of the crystal. The ions that come together to form these structures must be of opposite charges. This opposite-charge attraction forms the "glue" that holds these structures together.

By far the most common example of an ionic crystal is found in every household around the world: table salt or sodium chloride (NaCl). Table salt, also known as the mineral halite, is a simple ionic crystal that you can view in the multimedia presentation of this lesson.

Ionic crystals have definite properties that are similar for most examples of these salts and minerals. A mineral is a naturally occurring substance that is usually the combination of a metal and other atoms. A salt is an ionic compound of a metal (Na) and a nonmetal (Cl).

One property of ionic mineral crystals is that they are usually soluble in water, meaning that they dissolve into water to form solutions. Ionic crystals also form other important compounds, like acids and bases, which are water soluble and very reactive. Sometimes they are even dangerous, as in the case of strong acids like HCl or strong bases like NaOH.

Another property of ionic crystals is that when mixed with water, they dissociate, or split, into their component ions. With salt, the addition of water forms a salt water solution, where the ions Na⁺ and Cl^- are free-floating in the solution.