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 octahedral voids. What is the formula of the compound?

Let the no. of atoms of Y forming the ccp be x

So, the no. of octahedral voids = x

As the atoms of element Y forms ccp and atoms of X occupies all the octahedral voids, so the ratio of atoms of A and B are x:x

• A:B = 1:1

• The formula of the solid is AB