Question

The ionic radii of $R{b}^{+}$ and $I^{-}$ are $1.46$ and $2.16\stackrel{\circ }{A}$ respectively. The most probable type of structure exhibited by it is

• A. $CsCl$
• B. $NaCl$
• C. $ZnS$
• D. $Ca{F}_2$

Answer 1

The correct option is B $NaCl$

The most probable type of structure exhibited by $RbI$ is $NaCl$ type.
The radius ratio $\frac{r_{+}}{r_{-}}=\frac{1.46}{2.16}=0.676$. The radius ratio 0.414 to 0.732 corresponds to octahedral coordination.
NaCl forms fcc unit cell. Chloride ions form fcc arrangement and sodium ions occupy octahedral void.