How do ionic compounds form crystals?

A crystal lattice is a three dimensional array of ions.

for crystals by forming what is called a crystal lattice. The ions within the compound arrange themselves in a unique way as cool which gives each ionic compound a different crystal formation. There is a particular amount of energy given off when these form that is also unique to each crystal which is called the "crystal lattice energy."

The structure of the crystal lattice and the strength of it is related to the ions it is composed of. Generally, ions with larger charges will form stronger crystal lattices and so will ions of smaller size. If you think about this, it makes sense because larger charge means more electrical attraction between particles and smaller ionic size means greater proximity.