Crystalline solids are solids in which the particles (atoms, ions, or molecules) are arranged in a highly ordered, repeating three-dimensional pattern. They have a definite shape, sharp melting point, and well-defined structure.
Types of Crystalline Solids:
- Ionic Solids
- Constituents: Positive and negative ions
- Bonding: Ionic bonds
- Properties: Hard, brittle, high melting points, conduct electricity only when molten or in solution
- Examples: NaCl, KBr, MgO
- Molecular Solids
- Constituents: Molecules
- Bonding: Intermolecular forces (van der Waals, dipole–dipole, hydrogen bonding)
- Properties: Soft, low melting points, poor conductors
- Examples: Ice (H₂O), Dry ice (CO₂), Iodine (I₂)
- Metallic Solids
- Constituents: Metal atoms
- Bonding: Metallic bonds (sea of delocalized electrons)
- Properties: Malleable, ductile, good conductors of heat and electricity, lustrous
- Examples: Fe, Cu, Al, Au
- Covalent (Network) Solids
- Constituents: Atoms
- Bonding: Covalent bonds forming a continuous 3D network
- Properties: Very hard, high melting points, poor conductors (except graphite)
- Examples: Diamond (C), Quartz (SiO₂), Silicon (Si)