Question

What is the formula of a compound in which the element Y forms HCP lattice and atoms of X occupy ${\frac{2}{3}}^{rd}$ of tetrahedral voids?

Answer 1

Suppose the atoms Y in HCP = n

Number of tetrahedral voids = 2n

Number of atoms of $X=\frac{3}{2}\times 2n=\frac{4}{3}n$

$\therefore$ Ratio X and Y $=\frac{4}{3}n:n=4:3$

$\therefore$ Formula is $X_4{Y}_3$.