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:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(X_2Y\)
In a close-packed (ccp) arrangement of N atoms, the number of tetrahedral voids is 2N and the number of octahedral voids is N.
Let the number of Y atoms in the ccp lattice be N. Atoms of X occupy the tetrahedral voids:
\( \displaystyle \text{Atoms of X} = 2N \)
\( \displaystyle \text{X : Y} = 2N : N = 2 : 1 \)
So the formula of the compound is X2Y.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.