Question

A compound $M_p{X}_q$ has cubic close packing (ccp) arrangement of $X$. Its unit cell structure is shown below. The empirical formula of the compound, is

• A. $MX$
• B. $M{X}_2$
• C. $M_{2}X$
• D. $M_5{X}_{14}$

Answer 1

Answer: (B)

Contribution of atom from the edge centre is $1/4$. Therefore, number of
$M=\frac{1}{4}\times 4($ from edge centre $)+1($ from body centre $)=2$
Number of $X=\frac{1}{8}\times 8$ (from corners) $+\frac{1}{2}\times 6$
(from face centre) $=4$
$\Rightarrow$ Empirical formula $=M_2{X}_4=M{X}_2$