Question

A binary compound has Y-atoms forming FCC unit cell and another type of X-atoms occupying $\frac{1}{3}$rd of tetrahedral voids. Find out the molecular formula of the compound

Answer 1

For 1 unit cell,

No. of particles

X = $\frac{1}{3}\times8$

Y = 4

∴ The formula of Ionic solid = $X_{\frac{8}{3}}Y_4$ =$X_2Y_3$