Crystal lattice: definition in chemistry
Crystal lattice: The regular, repeating three-dimensional arrangement of particles (atoms, ions or molecules) in a crystalline solid.
The smallest repeating unit of a lattice is called the unit cell, and stacking unit cells in every direction builds the whole crystal. The arrangement of particles explains properties such as hardness, the way a crystal breaks and its melting point: ionic lattices like salt are hard and brittle with high melting points. Lattice energy measures how strongly the ions in an ionic lattice are held together.
Examples
- Table salt (NaCl) — a cubic lattice of Na⁺ and Cl⁻ ions
- Diamond — each carbon atom bonded to four others
- Ice — water molecules held in a hexagonal lattice by hydrogen bonds
- Copper — atoms packed closely in a regular metallic lattice
On the periodic table
Most metals crystallize in one of three lattice types (body-centered cubic, face-centered cubic or hexagonal close-packed), and the type changes from element to element across the table.