# Distinguish between

Question:

Distinguish between

(i)Hexagonal and monoclinic unit cells

(ii) Face-centred and end-centred unit cells.

Solution:

(i) Hexagonal unit cell

For a hexagonal unit cell,

$a=b \neq c$

and $\alpha=\beta=90^{\circ}$

$\gamma=120^{\circ}$

Monoclinic unit cell

For a monoclinic cell,

$a \neq b \neq c$

and $\alpha=\gamma=90^{\circ}$

$\beta \neq 90^{\circ}$

(ii) Face-centred unit cell

In a face-centred unit cell, the constituent particles are present at the corners and one at the centre of each face.

End-centred unit cell

An end-centred unit cell contains particles at the corners and one at the centre of any two opposite faces.