Question

A binary solid has zinc blend structure with $B^{-}$ ions constituting the lattice and $A^{+}$ ions occupying $25\%$ tetrahedral voids. The formula of solid is:

• A. $AB$
• B. $A_{2}B$
• C. $A{B}_2$
• D. $A{B}_4$

Answer 1

Answer: (C)

$A{B}_2$

Let the number of unit cells $=n$

Then, number of tetrahedral voids $=2n$

25% of tetrahedral voids $=\frac{25}{100}\times 2n=\frac{2n}{4}=\frac{n}{2}$

So the required formula is $A_{n/2}{B}_{n}orA{B}_2$