Question

A solid $AB$ has $NaCl$ structure. If the radius of cation $A^{+}$ is $170pm$, then the maximum possible radius of the anion $B^{-}$ is:

• A. $397.4pm$
• B. $347.9pm$
• C. $210.9pm$
• D. $410.6pm$

Answer 1

The correct option is D $410.6pm$

For $NaCl$ type structure $\frac{I_{A^{+}}}{I_{B^{-}}}=0.414-0.732$
For maximum possible radius of $B^{-}$

$\frac{I_{A^{+}}}{I_{B^{-}}}=0.414,\frac{170}{I_{B^{-}}}=0.414$

$I_{B^{-}}=\frac{170}{0.414}=410.6pm$.

Option D is correct.