Crystalline solid Definition: A Crystalline solid in which the constituent particles like atoms, ions or molecules are arranged definite repeating pattern through-out the solid is called crystalline solid.
Define crystalline Substances like solid sodium chloride (rock salt), potassium chloride, potassium nitrate (nitre), diamond, graphite etc., are some typical crystalline solids. All crystalline solids show the following properties:
- 1} All crystalline solids possess characteristic geometrical shapes.
- 2} the mechanical, optical and electrical properties of crystalline solids depend upon the direction along which these are measured, i.e., crystalline solids are anisotropic.Diamond and graphite are crystalline solids.
- 3} the constituent particles in crystals are generally held by strong inter atomic, inter ionic or intermolecular forces. Particles in a solid do not possess translational motion, but they can vibrate about their equilibrium positions.
- 4} Crystalline solids have sharp melting points. This indicates that there exists a long-range order in the crystalline solids. The long-range order in crystalline solids due to a regular arrangement of the constituent particles (atoms, ions or molecules) in three dimensions. For example, in a crystal of sodium chloride, experiments have shown that Na+ and Cl- ions are located at alternate sites. Each Na+ ion is surrounded by a fixed number (six) of Cl- ions and vice-versa.The three-dimensional order in NaCl crystals is due to the strong columbic attraction between Na+ and Cl- ions. A similar regular arrangement is also found in other solids. This means that in crystalline solids the particles are arranged in almost perfect order.
- 5} each particle in a crystalline solid has the same arrangement of particles around it through the types of crystals.
- 6} When cut or hammered gently, crystalline solids show a clean cleavage, i.e., they show fracture along a smooth surface. Diamond is a crystalline solid. When hammered gently, diamond gets cleaved smoothly along certain preferred directions. Hammer gently a big crystal of rock salt ( sodium chloride ). The big crystal gets broken down into smaller crystals with smooth surfaces.