Question

In a cubic structure of compound which is made from X and Y, where X atoms are at the corners of the cube and Y at the face centres of the cube. The molecular formula of the compound is.

• A. $X_{2}Y$
• B. $X_{3}Y$
• C. $XY_{2}$
• D. $XY_{3}$

Answer 1

Answer: (D)

$XY_{3}$

Answer 2

X atoms are at eight corners of the cube. Therefore, the number of X atoms in the unit cell $= \frac{8}{8} = 1$.

Y atoms are at the face centre of six faces. Therefore, its share in the unit cell $= \frac{6}{2} = 3$. The formula is $XY_{3}$.