Question

If the radius of $C{s}^{+}=1.69A^{\circ }\&Br–=1.95A^{\circ },$ then which of the following is correct statement?

• A. Edge length of unit cell is $4.2A^{\circ }$
• B. Coordination number for $C{s}^{+}$ is $6$
• C. $B{r}^{–}$ is present in void
• D. $CsBr$ has $FCC$ type structure

Answer 1

The correct option is A Edge length of unit cell is $4.2A^{\circ }$

$\frac{R_{c{s}^{+}}}{R_{B{r}^{-}}}=\frac{1.69}{1.95}=0.87$

Since, this ratio lies in the range $0.732–1.000,$ the $C{s}^{+}$ ion lies in the cubical void formed by $B{r}^{–}$ ions which forms simple cubic unit cell.