Question

A solid crystal is composed of X, Y and Z atoms. Y atoms are occupying 50% of octahedral voids, whereas X atoms are occupying the 100% tetrahedral void with Z atoms present in the ccp array arrangement, then the formula of the compound in the given crystal is

• A. $X_{4}Y{Z}_2$
• B. $X_5{Y}_{10}{Z}_8$
• C. $X_{3}Y{Z}_2$
• D. $X{Y}_4{Z}_2$

Answer 1

The correct option is A $X_{4}Y{Z}_2$

Total number of atoms in ccp is 4. Number of octahedral voids is 4 and tetrahedral voids is 8.

Given,
Y occupies 50 % of the octahedral voids and hence the number of atoms is 2.
X ocupies 100 % of the tetrahedral voids and hence the number of atoms is 8.
Z occupies the ccp position and hence the number of atoms is 4

X: Y : Z = 8:2:4 = 4:1:2