Question

In a face centered cubic lattice atoms $A$ are at the corner points and atoms $B$ at the face centered points. If atom $B$ is missing from one of the face centered points, the formula of the ionic compound is :

• A. $AB_2$
• B. $A_5B_2$
• C. $A_2B_3$
• D. $A_2B_5$

Answer 1

Answer: (D)

$A_2B_5$

Answer 2

$A=8\times\frac{1}{8}=1$
$B=6\times\frac{1}{2}-1\times\frac{1}{2}=\frac{5}{2}$
$A : B$
$1:\frac{5}{2}$
$\Rightarrow 2:5$