Crystalline Solids have a well-defined, repeating atomic structure extending in all three spatial dimensions.
Characteristics:
Long-Range Order: Atoms or molecules are arranged in a repeating pattern.
Anisotropy: Physical properties depend on the direction due to the ordered structure.
Sharp Melting Point: Crystalline solids melt at a specific temperature.
Types of Crystals:
Ionic Crystals:
Composed of ions held together by electrostatic forces.
Example: Sodium chloride (NaCl).
Covalent Crystals:
Atoms are connected by covalent bonds in a continuous network.
Example: Diamond (carbon).
Metallic Crystals:
Metal atoms sharing a "sea" of electrons, allowing conductivity.
Example: Iron (Fe).
Molecular Crystals:
Molecules held together by intermolecular forces such as hydrogen bonds and van der Waals forces.
Example: Ice (H₂O).
Applications of Solid - Crystalline:
Electronics: Semiconductor crystals like silicon.
Optics: Crystals used in lasers and lenses.
Materials Science: Understanding properties like hardness and conductivity.