Question

Which of the following expressions is correct in case of a $CsCl$ unit cell (edge length, $a$ ) ?

• A. $r_{c}+r_{a}=a$
• B. $r_{c}+r_{a}=\frac{a}{\sqrt{2}}$
• C. $r_{c}+r_{a}=\frac{\sqrt{3} a}{2}$
• D. $r_{c}+r_{a}=\frac{a}{2}$

Answer 1

Answer: (C)

In $CsClCs^{+} \rightarrow $ at body center
$Cl^{-} \rightarrow $ at every corner
$2\left(r_{c} + r_{a}\right)=\sqrt{3}a$ (along body diagonal)
$rc+ra=\frac{\sqrt{3} a}{2}$