Among the following which one has the highest cation to anion size ratio?
Among the following which one has the highest cation to anion size ratio?
$\mathrm{CsI}$
CsF
$\mathrm{LiF}$
$\mathrm{NaF}$
Solution
The order of size of given cations is
$\mathrm{Li}^{+} < \mathrm{Na}^{+} < \mathrm{Cs}^{+}$
and the order of size of given anions is
$\mathrm{I}^{-} > \mathrm{F}^{-}$
Thus, when the cation is largest and anion is smallest, the cation to anion size ratio is maximum.
Hence, cation to anion size ratio is maximum for CsF.