Solid - Crystalline

• 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.