Question

Which of the following compounds has the lowest melting point?

• A. $CaC{l}_2$
• B. $CaB{r}_2$
• C. $Ca{I}_2$
• D. $Ca{F}_2$

Answer 1

The correct option is C

$Ca{I}_2$

The cation is the same in each case. The anions are from the halgen group. As we go down this group, the ionic radius of the anion increases for the same charge. For this reason, the charge in $I^{-}$ is more spread out and hence large ions tend to be easily polarizable. In other words, their electron cloud is easily skewed. More the polarizability of the anion – the greater is the covalent character. Hence calcium iodide has the highest covalent character (among the given compounds that is!). Higher the covalent character, the lower the melting point.