iodine (I) /ī′ədīn/ [Gk, ioeides, violet] , a nonmetallic element of the halogen group. Its atomic number is 53; its atomic mass is 126.90. Iodine is a bluish black solid that becomes a violet vapor on heating without going through a liquid phase. Iodine is an essential micronutrient or trace element. Almost 80% of the iodine present in the body is in the thyroid gland, mostly in the form of thyroglobulin. Iodine deficiency can result in goiter or cretinism. Iodine is found in seafood, iodized salt, and some dairy products. It is used as a contrast agent for blood vessels in computed tomography scans. Radioisotopes of iodine are used in radioisotope scanning procedures and in palliative treatment of cancer of the thyroid.
