Chemistry

The color of ionic compounds depends on which ion absorbs visible light. Here, iodide ($\text{I}^-$) is a large, easily polarizable anion that absorbs light in the visible range, giving $\text{CdI}_2$ its pink color. Chloride ($\text{Cl}^-$) is much smaller and less polarizable, so it doesn't absorb visible light the same way. Since the cadmium cation ($\text{Cd}^{2+}$) is colorless and chloride doesn't contribute color, $\text{CdCl}_2$ will be colorless or white.

The color of ionic compounds depends on which ion absorbs visible light. Here, iodide ($\text{I}^-$) is a large, easily polarizable anion that absorbs light in the visible range, giving $\text{CdI}_2$ its pink color. Chloride ($\text{Cl}^-$) is much smaller and less polarizable, so it doesn't absorb visible light the same way. Since the cadmium cation ($\text{Cd}^{2+}$) is colorless and chloride doesn't contribute color, $\text{CdCl}_2$ will be colorless or white.