Crystalline
Definition and meaning of Crystalline in chemistry.
Crystalline describes a solid in which atoms, ions, or molecules are arranged in a highly ordered, repeating three-dimensional pattern known as a crystal lattice.
In more detail
This long-range order produces macroscopic crystals with flat faces meeting at characteristic, fixed angles, and gives crystalline solids a sharp, well-defined melting point rather than a gradual softening range. The repeating lattice also diffracts X-rays in a distinct pattern, which is the basis of X-ray crystallography for determining atomic structure. Crystalline solids are classified by their unit cell geometry (cubic, tetragonal, hexagonal, etc.) and stand in contrast to amorphous solids, which lack this long-range order.
Key facts
| Field | General Chemistry |
|---|---|
| Opposite | Amorphous (no long-range order) |
| Common example | NaCl (sodium chloride) |
| Key property | Sharp, definite melting point |
Sodium chloride (table salt) is crystalline: its Na+ and Cl- ions alternate in a repeating face-centered cubic lattice, producing cube-shaped crystals and a sharp melting point of 801°C.
Frequently asked questions
How is a crystalline solid different from an amorphous solid?
A crystalline solid has atoms or ions arranged in a repeating, long-range order and melts sharply at a fixed temperature, while an amorphous solid (like glass) lacks long-range order and softens gradually over a range of temperatures.
How do scientists determine a crystalline structure?
Chemists use X-ray crystallography, in which X-rays scattered by the ordered lattice produce a diffraction pattern that reveals the positions of atoms within the unit cell.