Question

For potassium chloride (KCl), calculate the radius ratio to show why the compound has the cesium chloride structure.

Answer 1

Explanation:

The radius for potassium ion, ${r^+}$  = 152 pm

The radium for the chloride ion, ${r^-}$  = 167 pm

$\frac {r^+}{r^-}=\frac {152}{167}=0.91018$

Cesium chloride has cubic unit cell and for the ionic compounds to have such lattice, the condition is:

${\frac {r^+}{r^-}}\geq 0.732$

Thus, for potassium chloride, the ratio is 0.91018 and it is greater than 0.732. It exists in the cesium chloride structure.