Crystal Lattice
Definition and meaning of Crystal Lattice in chemistry.
A crystal lattice is the ordered, repeating three-dimensional arrangement of points that represents the positions of atoms, ions, or molecules in a crystalline solid.
In more detail
The lattice itself is a geometric abstraction: an infinite array of points related by translational symmetry. The actual solid is built by attaching a repeating group of atoms or ions, called the basis, to every lattice point. The smallest repeating block that reproduces the whole lattice by translation alone is the unit cell, and stacking unit cells in three directions generates the full crystal. There are exactly 14 distinct three-dimensional lattice types, the Bravais lattices, grouped into seven crystal systems (cubic, tetragonal, orthorhombic, and so on).
Key facts
| Field | General Chemistry |
|---|---|
| Formula (example) | NaCl |
| Number of Bravais lattices | 14 (in 7 crystal systems) |
| Repeating unit | Unit cell |
Sodium chloride (NaCl) forms a face-centered cubic lattice in which Na+ and Cl- ions alternate at lattice positions, giving the familiar rock-salt structure with each ion surrounded by six oppositely charged neighbors.
Frequently asked questions
Is a crystal lattice the same as a crystal structure?
Not exactly. The lattice is an abstract array of geometric points; the crystal structure results when a specific basis of atoms or ions is placed at each lattice point.
How does a unit cell relate to the crystal lattice?
The unit cell is the smallest repeating block of the lattice; translating it repeatedly in three dimensions reproduces the entire crystal lattice.