CBSE Class 12 Chemistry Chapter 1 Revision Notes

Chapter 1: The Solid State Revision Notes

  • Solids are materials with a definite shape and volume.
  • Rigidity, incompressibility, slow diffusion, and mechanical strength characterize them.
  • Solids are categorized as crystalline solids amorphous solids.


Types of Crystalline Solids

  • Crystalline solids are of 4 types – ionic solids, covalent solids, molecular solids, metallic solids


Crystal Lattices

  • The pattern formed by the points is known as the crystal lattice.
  • These points are used to represent the positions of the repeating structural elements.
  • A lattice is the best way to describe the periodic structure of an ideal crystal.
  • The crystal lattice is a three-dimensional symmetrical structural arrangement of atoms, ions, or molecules (constituent particles) as points inside a crystalline solid.
  • It is a geometrical arrangement of atoms, ions, or molecules of a crystalline solid as points in space.
  • A single point represents each atom, molecule, or ion (constituent particle) in a crystal lattice.
  • The term lattice site or lattice point refers to these points.
  • In a crystal lattice, a straight line connects the lattice sites or points.
  • We can get a three-dimensional view of the structure by connecting these straight lines.
  • This three-dimensional arrangement is called Bravais Lattices.

Unit Cell

  • The tiniest of a crystal lattice is the unit cell.
  • In a crystal structure, it is the simplest repeating unit.
  • The unit cell is repeated in different directions to create the entire lattice.

Types of Unit Cells


Close Packing

  • The space efficient arrangement of the constituent particles in a crystal lattice is known as close packaging.
  • To better comprehend this packing, we must assume that all particles (atoms, molecules, and ions) have the same spherical solid shape.
  • As a result, the lattice’s unit cell is cubic in shape.
  • There will always be some empty spaces in the cell when we stack the spheres.
  • The arrangement of these spheres must be very efficient in order to minimize these empty spaces.
  • To avoid empty spaces, the spheres should be arranged as close together as possible.


One Dimension

  • The spheres (i.e. the atoms) are arranged in a row in this arrangement.
  • All of the spheres are tightly packed and in close proximity to one another.
  • As a result, one sphere is in contact with the other sphere on both sides.
  • So there are two spheres or particles in close proximity to each other.
  • As a result, the one-dimensional structure’s coordination number is 2.

Two and Three Dimension


Imperfections in Solids

  • Any irregularities in the pattern of crystal arrangement in a solid lattice leads to imperfection in the solid.
  • These defects occur when crystallization happens very fast.
  • This is mainly due to the limited amount of time for particles to arrange themselves in a regular pattern.


Electrical and Magnetic Properties



The Solid Stat The Solid State – NCERT


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