Question

A solid is formed and it has three types of atoms X, Y and Z. X forms FCC lattice with Y atoms occupying all the tetrahedral voids and Z atoms occupying half the octahedral voids. If the formula of the solid is $X_a{Y}_b{Z}_c$, then the values of a, b and c are, respectively :

• A. $1,2,4$
• B. $2,4,1$
• C. $4,1,2$
• D. $1,4,2$

Answer 1

Answer: (B)

$2,4,1$

Number of X atoms $=(\frac{1}{8}\times 8)+(\frac{1}{2}\times 6)=4$
Number of Y atoms $=8$
Number of Z atoms $=\frac{1}{2}\times 4=2$
Hence the formula of the compound is $X_2{Y}_4{Z}_1$