question_answer

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

A) \[{{r}_{Cs}}+{{r}_{C{{l}^{-}}}}=3a\]

B) \[{{r}_{Cs}}+{{r}_{C{{l}^{-}}}}=\frac{3a}{2}\]

C) \[{{r}_{Cs}}+{{r}_{C{{l}^{-}}}}=\frac{\sqrt{3}}{2}a\]

D) \[{{r}_{Cs}}+{{r}_{C{{l}^{-}}}}=\sqrt{3}a\]

Correct Answer: C

Solution :

[c] Relation between radius of cation, anion and edge length of the cube \[2{{r}_{Cs}}+2{{r}_{C{{l}^{-}}}}=\sqrt{3}a\] \[{{r}_{C{{s}^{+}}}}+{{r}_{C{{l}^{-}}}}=\frac{\sqrt{3}a}{2}\]