Why does iodine have a much lower melting point than sodium iodide? Why does iodine have a much lower melting point than sodium iodide? Solution Iodine occurs in a solid form and it is comprised of molecular bonds. In case of NaI, it is comprised of corresponding ionic bonds. The lattice structure is formed in 1:1 ratio that means that for each Na + there exists I - Hence the interaction will be stronger and in order to melt the crystal structure of NaI, all the ionic bonds need to be broken which results in high energy consumption. Therefore, NaI has a higher melting point than Iodine. .