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

Explanation

The cc p lattice is formed by the element `Y`.
First method
`:. Z_(eff)` of `Y` (as anions) `= 4`
Number of `TV_(s) = 8//"unit cell"`
Number of `OV_(s) = 4`/unit cell
Since all the `OV_(s)` are occupied by `X`.
`:.` Number of `X` (as cations) `= 4`.
`:.` Formula `= X_(4) Y_(4) = 4XY`
Second method
Let `Z_(eff)` of `Y` (as anions) `= 1`
Number of `TV_(s) = 2//"atom"` or anion
Number of `OV_(s) = 1//"atom"` or anion.
Since all the `OV_(s)` are occupied by `X`.
`:.` Number of `X` (as cations) `= 1`.
`:.` Formula `= XY`