Question

$CsCl$ crystallises in body centred cubic lattice. If $a$ is its edge length, then which of the following expressions is correct?

• A. $r_{C{s}^{+}}+r_{C{l}^{-}}=\frac{\sqrt{3}}{2}a$
• B. $r_{C{s}^{+}}+r_{C{l}^{-}}=\sqrt{3}a$
• C. $r_{C{s}^{+}}+r_{C{l}^{-}}=3a$
• D. $r_{C{s}^{+}}+r_{C{l}^{-}}=\frac{3a}{2}$

Answer 1

The correct option is A $r_{C{s}^{+}}+r_{C{l}^{-}}=\frac{\sqrt{3}}{2}a$

In $CsCl$ structure, $C{s}^{+}$ ion is in contact with $C{l}^{-}$ ion at the nearest distance which is equal to $\frac{\sqrt{3}a}{2}$.