Distinguish between
a. Hexagonal and monoclinic unit cells
(b) Face-entred and end-centred unit cells

Explanation

(i) Hexagonal unit cell has two edges of equal length `(a = b != c) ` while monoclinic unit cell has all the three edges of unequal length `(a != b != c)`.
In hexagonal two angles are of `90^@` and one angle of `120^@ (alpha = beta = 90, gamma = 120)`. In monoclinic , two angles are of `90^@` but one is not of `90^@ (alpha = gamma = 90^@, beta != 90^@)`
(ii) Face centred unit cell has points at the corners as well as the centre of each face. It has 4 atoms per unit cell.
End centred unit cell has points at all the corners and at the centre of any two opposite faces. It has 2 atoms per unit cell.