Final answer:
A crystal is the structure formed when ions arrange themselves in an orderly manner. It consists of alternating positive and negative ions held together by ionic bonds.
Step-by-step explanation:
The structure formed when ions arrange themselves in an orderly manner is known as a crystal. Crystals are formed from a combination of positively-charged cations and negatively-charged anions held together by ionic bonds. They have a regular, three-dimensional array of alternating positive and negative ions.