A compound is formed by two elements X and Y. Atoms of 'Y' make ccp and those of element 'X' occupy tetrahedral voids. The formula of the compound is:

\(X_2Y\)

The correct answer is option 2. \(X_2Y\).

In a close-packed structure like CCP (cubic close-packed) or FCC (face-centered cubic), each sphere (or atom) touches six neighboring spheres (or atoms) in its layer and three in each of the layers above and below it. This arrangement creates tetrahedral and octahedral voids within the structure.

Given that atoms of element Y make CCP and those of element X occupy tetrahedral voids, the ratio of atoms X to Y in the compound can be determined based on the number of tetrahedral voids filled by X atoms compared to the number of atoms Y in the CCP lattice.

In a CCP lattice, each sphere (atom) occupies one corner of a cube and one at the center of each face. Thus, in one unit cell of CCP, there are 8 corner atoms × 1/8 + 6 face-centered atoms × 1/2 = 4 atoms. In a CCP structure, the number of tetrahedral voids is twice the number of atoms. Therefore, the number of tetrahedral voids is 8.

Now, the atoms of element X occupy all the tetrahedral voids, and each tetrahedral void is occupied by one atom. So, the number of atoms of element X in the compound is also 8.

Hence, the ratio of X to Y in the compound is 8:4, which simplifies to 2:1.

Therefore, the formula of the compound is \( X_2Y \).

So, the correct answer is option 2: \(X_2Y\).