Question

In a face centered lattice of X and Y, X atoms are present at the corners while Y atoms are at face centers. Then the formula of the compound would be if one of the X atoms is missing from a corner in each unit cell:
A. `X_(7)Y_(24)`
B. `X_(24)Y_(7)`
C. `XY_(24)`
D. `X_(24)Y`

Answer 1

Correct Answer - A
No. of X atom per unit cell `= 7 xx (1)/(8) = (7)/(8)`
No. of Y atom per unit cell `= 6 xx (1)/(2) = 3`
`:.` Formula `= X_(7//8) Y_(3) " or " X_(7) Y_(24)`