Question

The number of tetrahedral voids per unit cell in NaCl crystal is ......

(a) 4

(b) 8

(c) twice the number of octahedral voids

(d) four times the number of octahedral voids

Answer 1

Answers: (b), and (c)

NaCI has a rock salt type structure having an fcc arrangement. It means the NaCl has the fcc arrangement of CF ions.

Total number of atoms per nuit cell =4

$\therefore$ Number of tetrahedral voids = $2\times 4=8$

Number of octahedral voids = 4

Hence, (b) and (c) are correct choices.