About Iodides

Arsenic Iodide

Iodides are compounds containing the iodine anion, I-. Iodides include salts such as sodium iodide and organic compounds such as methyl iodide.

Iodide is one of the largest anions. With a radius estimated at 220 picometers, it is the larger than bromide (196 pm), chloride (181 pm), and fluoride (133 pm) ions. In part because of its size, iodine forms relatively weak bonds with most elements. Most iodide salts are soluble in water, but often less so than the related chlorides and bromides. Iodide, being large, is less hydrophilic than the smaller anions. One consequence is that sodium iodide is highly soluble in acetone, whereas sodium chloride is not. The low solubility of silver iodide and lead iodide reflect the covalent character of these metal iodides. Iodides are common in everyday life; for example potassium iodide is the iodine component of iodized salt and silver iodide is a photoactive component of silver-based photographic film.