Ncert Exercises & Solutions

22. In terms of band theory, what is the difference

(i) Between a conductor and an insulator

(ii) Between a conductor and a semiconductor

For a face-centred unit cell:

a = 2 \sqrt{2} r

It is given that the atomic radius, r = 0.144 nm
So,

a = 2 \sqrt{2} \times 0.144 nm = 0.407 nm

Hence, length of a side of the cell = 0.407 nm