Question

A compound is formed by two elements X and Y. Atoms of the element Y (as anions) make ccp and those of the element X (as cations) occupy all the octahedral voids. What is the formula of the compound?

• A. $XY$
• B. $X_2Y$
• C. $XY_2$
• D. $XY_3$

Answer 1

Answer: (A)

$XY$

Answer 2

The ccp lattice is formed by the element $Y$. The number of octahedral voids generated would be equal to the no of atoms of $Y$ present in it. Since all the octahedral voids are occupied by the atoms of $X$, the number would also be equal to that of the element $Y$. Therefore the formula of the compound is $X Y$.