Why is iodine, a group 7 element, soluble in water?
Iodine isnt particularly soluble in water. In fact its solubility in pure water is very similar to that of bromine and chlorine. I suspect that you are asking this question because you have seen, or used, a deep brown solution labelled I2(aq) or, at any rate, you have been told to use an aqueous solution of iodine. In reality, this is not a solution of iodine in water, because, as I have mentioned above, iodine doesnt dissolve to any extent in water. What is being used is a solution of iodine in aqueous potassium iodide. You probably werent told this! Iodide ions in aqueous potassium iodide reacts with iodine molecules and converts them into a soluble complex – the tri-iodide ion.
