Crystal (crystalline solid)

Crystalline solids consist of atoms, ions and molecules arranged in a definite and repeating three-dimensional pattern in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions in a definite repeating pattern.

Unlike amorphous solids that melt at a range of temperatures, crystalline solids have definite melting points. Crystalline solids include metallic, ionic, network atomic and molecular solids, and true solids are crystalline.

Characteristics of crystalline solids

Samples of crystalline solids. Photo by Franco Antonio Giovanella on Unsplash

The main characteristics of crystalline solids are mentioned as below:

  • Crystalline solids show a regular structure and have a definite geometrical shape.
  • The sharp freezing point is found in crystalline solids. This is because the distance between the same atoms/molecules or ions is the same and remains constant, unlikely from amorphous solids.
  • The heat of fusion is definite and fixed as the regularity in crystal lattice remains the same and is ideal.
  • Crystalline solids are also known as true solids as they don’t tend to flow like pseudo-solids.
  • When we cut a crystal solid with a knife, we obtain a flat and smooth surface.
  • The nature of crystalline solid is anisotropic; that is, the properties turn out to be different in a different direction.
  • Crystalline solids depict both long-range and short-range order.

A single macroscopic crystal is usually identifiable by their geometrical shape, consisting of flat faces with specific, particular orientations.

The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.

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