Crystalline solids are classified based on the type of bonding between their constituent particles:

• Molecular Solids: Held together by weak intermolecular forces (Van der Waals, dipole-dipole, or hydrogen bonds). They are generally soft and have low melting points.
  • Non-polar Molecular Solids: (e.g., Argon, Iodine) Held by London Dispersion Forces.
  • Polar Molecular Solids: (e.g., Solid SO2, Solid NH3) Held by Dipole-Dipole interactions.
  • Hydrogen-Bonded Molecular Solids: (e.g., Ice) Held by Hydrogen bonds.
• Ionic Solids: Held together by strong electrostatic forces between oppositely charged ions. They are hard, brittle, and have high melting points. Example: NaCl, MgO.
• Metallic Solids: Held together by metallic bonds (a sea of delocalized electrons surrounding positive metal ions). They are good conductors of heat and electricity, malleable, and ductile. Example: Copper, Iron, Silver.
• Covalent or Network Solids: Atoms are linked by a network of covalent bonds throughout the crystal. They are very hard and have extremely high melting points. Example: Diamond, Graphite, Quartz (SiO2).