Question

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

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

Answer 1

Answer: (C)

Relation between radius of cation, anion and edge length of the cube
$2 r _{ Cs^+}+2 r _{ Cl^- }=\sqrt{3} a$
$r _{ Cs ^+}+ r _{ Cl ^-}=\frac{\sqrt{3} a}{2}$