Question

# Cesium chloride on heating to $760{\text{K}}$ changes into:A.${\text{CsCl}}\left( {\text{g}} \right)$B.${\text{NaCl}}$ structureC.Antifluorite structureD.${\text{ZnS}}$ structure

The chemical formula of cesium chloride is ${\text{CsCl}}$ , it is an inorganic ionic compound. It is present as impurities in ore such as carnallite, sylvite and kainite. Its molar mass is $168.36{\text{gmo}}{{\text{l}}^{ - 1}}$ with a melting and boiling point of ${646^o}{\text{C and }}{1297^o}{\text{C}}$ respectively.
The reason for changing cesium chloride structure to sodium chloride structure on heating the cesium chloride structure at $760{\text{K}}$ is due to size difference between the ions. This can be understood as, when the size difference between the ions is small or we can say both the ions are similar in size then cesium chloride structure is adopted by the crystal. If the size difference between the ions is large or both the ions are not similar in size then sodium chloride structure is adopted by the lattice. As we can see, in case of cesium chloride, the ionic radius of cesium is 174pm and ionic radius of chloride is 181pm which is of similar size but in sodium chloride, ionic radius of sodium ion is 102pm and ionic radius of chloride is 181pm which is not similar to each other.