0Classification of Crystalline Solids
Based on the nature of intermolecular forces, crystalline solids are classified into four categories −
Molecular solids
- Ionic solids
- Metallic solids
- Covalent solids
- Molecular solids
- Constituent particles are molecules
Ionic solids
- Constituent particles are ions
- Hard but brittle
- Insulators of electricity in solid state, but conductors in molten state and in aqueous solution
- High melting point
- Attractive forces are Coulombic or electrostatic
- Example − NaCl, MgO, ZnS
- Metallic solids
- In metallic solids, positive ions are surrounded and are held together in a sea of delocalised electrons.
- Hard but malleable and ductile
- Conductors of electricity in solid state as well as molten state
- Fairly high melting point
- Particles are held by metallic bonding
- Example − Fe, Cu, Mg
- Covalent or network solids
- Constituent particles are atoms
- Hard (except graphite, which is soft)
- Insulators of electricity (except graphite, which is a conductor of electricity)
- Very high melting point and can decompose before melting
- Particles are held by covalent bonding
- Example − SiO2 (quartz), SiC, diamond, graphite
