Question

What are the types of unit cells?

Answer 1

Hint: This question is based on the concept of unit cells in molecular chemistry. Unit cell is the smallest repeating unit of a crystal lattice, that builds up a crystal of substance.

Complete answer: The identical unit cells are identified in such a way that they fill the available space without overlapping. A crystal lattice is a three-dimensional arrangement of atoms, molecules, or ions within a crystal. It consists of a large number of unit cells. Per lattice point is occupied by one of the three constituent particles.
Primitive cubic unit cell:
Atoms are only present at the corners of the primitive cubic unit cell. Every atom in the corner is shared by eight unit cells next to it. In the same layer, there are four unit cells, and four in the upper (or lower) layer. As a result, each unit cell contains just 1/8th of an atom.
Body-centred cubic unit cell:
A BCC unit cell has an atom in the centre of the structure and atoms at each corner of the cube. An open structure is depicted in the diagram below. The atom at the centre of the body, according to this structure, belongs entirely to the unit cell in which it is found.
Face-centred cubic unit cell:
An FCC unit cell has atoms at all four corners of the crystal lattice, as well as in the centre of each of the cube's faces. Just 1/2 of each atom belongs to an individual cell, and the atom present at the face-centered is shared by two adjacent unit cells.

Note:
Cubic, tetragonal, orthorhombic, hexagonal, monoclinic, tri clinical, and rhombohedral are seven simple crystal structures. Their crystallographic axes and angles are arranged differently. According to the above seven, Bravis described 14 possible crystal systems.