Unit Cell – Definition and Types

What is a Unit Cell?

A unit cell is the smallest repeating unit of a crystal lattice. It is a three-dimensional shape with sides that are all the same length and angles that are all the same size.

Types of Unit Cell

There are six types of unit cells:

1. The simplest type of unit cell is the primitive cell, which has six corners and no sides. All other unit cells are derived from the primitive cell by adding sides or corners.
2. The next simplest type of unit cell is the square cell, which has four sides and eight corners.
3. The next simplest type of unit cell is the rectangular cell, which has six sides and twelve corners.
4. The next simplest type of unit cell is the hexagonal cell, which has six sides and twelve corners.
5. The next simplest type of unit cell is the cubic cell, which has eight sides and sixteen corners.
6. The most complex type of unit cell is the tetragonal cell, which has four sides and eight corners.

What is the Basic Unit of Life?

The basic unit of life is the cell. Cells are the smallest living unit and are the building blocks of all life. Cells are made up of molecules and are enclosed by a membrane. They contain DNA, which stores the genetic information of the organism. Cells can divide and produce new cells, which can then divide and produce new cells, and so on. This process is called cell division and is how organisms grow and reproduce.

Classification of Crystal Structure by Symmetry

There are seven classes of crystal structure by symmetry, which are shown in the table below. The class is determined by the number of axes of rotational symmetry and the number of mirror planes. For example, a crystal with one axis of rotational symmetry and one mirror plane is a tetragonal crystal.