Question

In a compound, atoms of element Y form ccp lattice and those of element X occupy $\frac{2}{3}$ rd tetrahedral voids. The formula of the compound will be:

• A. $X_3{Y}_4$
• B. $X_4{Y}_3$
• C. $X_2{Y}_3$
• D. $X_{2}Y$

Answer 1

The correct option is B $X_4{Y}_3$

Let no. of atoms of Y used in packing = n
No. of tetrahedral voids = 2n
No. of atoms of $x=\frac{2}{3}\times 2n=\frac{4}{3}n$
$Y:X=n:\frac{4}{3}=3:4$
Formula = $X_4{Y}_3$