Classification of solids

Classification of Solids

Solids are materials that maintain a fixed shape and volume. Depending on how their particles are arranged and the types of intermolecular forces acting between them, solids are generally grouped into two major categories: Crystalline solids and Amorphous solids. Crystalline solids can be further classified based on the nature of the forces that hold their particles together.

1. Crystalline Solids

Crystalline solids are solids in which the constituent particles are arranged in a definite repeating pattern throughout the solid. They have a well-defined geometric shape, sharp melting points, and distinct cleavage planes.

Types of Crystalline Solids

• Ionic Solids: Formed by electrostatic attraction between oppositely charged ions. Example: NaCl, KBr.
• Molecular Solids: Formed by molecules held together by van der Waals forces, dipole-dipole interactions, or hydrogen bonds. Example: Ice, CO₂, Iodine.
• Covalent (Network) Solids: Atoms are connected by a continuous network of covalent bonds. These solids are hard and have high melting points. Example: Diamond, Quartz (SiO₂).
• Metallic Solids: Made up of metal atoms immersed in a sea of free-moving electrons. These solids efficiently conduct heat and electricity due to the mobility of the electrons. Example: Iron, Copper, Silver.

2. Amorphous Solids

Amorphous solids, also known as pseudo solids or supercooled liquids, lack a regular or orderly arrangement of their constituent particles. Their structure is irregular and they melt over a range of temperatures.

• They lack a long-range order in the arrangement of particles.
• Do not have sharp melting points.
• Examples include glass, plastic, and pitch.

Comparison Between Crystalline and Amorphous Solids