The Solid State Class 12 Notes - Chapter 1

Solids have definite volume, shape, and mass due to the short distance between the fixed position of particles and strong interactions between them. Amorphous solids behave like super cool liquids as the arrangement of constituent particles has short-range order, isotropic in nature and no sharp melting point. Crystalline solids have a characteristic shape, with the arrangement of constituent particles of long-range order, anisotropic in nature and a sharp melting point. The classification of crystalline solids is based on their property. The crystalline property depends on the nature of interactions between the constituent particles, and therefore these solids are divided into four different categories:

  • Ionic solids
  • Covalent solids
  • Molecular solids
  • Metallic solids

Bravais Lattices

In crystalline solids, the arrangement of constituent particles is seen in a regular pattern that extends throughout the solid crystal. This arrangement is represented by crystal lattice which is a three-dimensional array of points. 14 different kinds of lattices are possible called Bravais lattices.

Types Of Unit Cell

A lattice can be generated by repeating a small portion called the unit cell. Below are some of the different varieties of unit cell:

  • Simple cubic
  • Face-centered cubic
  • Body-centered cubic

Few Important Questions

  1. Explain the term coordination number.
  2. Distinguish between Cubic close-packing and Hexagonal close-packing.
  3. Explain why Ionic solids are brittle and hard.
  4. Distinguish between a semiconductor and a conductor?
  5. Explain Paramagnetism with suitable example.

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Practise This Question

The half - time period of a radioactive element is 140 days. After 650 days, one gram of the element will reduce to (J 1986)