Naturally-occurring iodine is a single isotope with 74 neutrons. Chemically, iodine is the second least reactive of the halogens, and the second most electropositive halogen, trailing behind astatine in both of these categories.

Potassium iodide is an inorganic compound with formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with.

Povidone-iodine (PVP-I) is a stable chemical complex of polyvinylpyrrolidone (povidone, PVP) and elemental iodine. It contains from 9.0% to 12.0% available iodine, calculated on a dry basis