What is the term for a solid formed by a geometric arrangement of ions?

The term for a solid formed by a geometric arrangement of ions is the Crystal Lattice. In a crystal lattice, ions are arranged in a repeating three-dimensional pattern that maximizes the attractive forces between oppositely charged ions while minimizing the repulsive forces between ions of the same charge. This specific arrangement is characteristic of ionic compounds, leading to their stability and distinct physical properties, such as high melting points and the ability to conduct electricity when melted or dissolved in water.

The concept of a crystal lattice is foundational to understanding ionic bonding and the structure of many minerals and salts. In contrast, a molecule refers to a group of atoms bonded together covalently, which pertains to different types of compounds. Atomic structure deals with the arrangement of protons, neutrons, and electrons in an atom, while an ion pair refers to two ions that are attracted to each other, but it does not encompass the extensive geometric arrangement that defines a crystal lattice.