# 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.

## 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.

## 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.

## Source:

The Solid Stat The Solid State – NCERT

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