Iodine-131 bioaccumulation in regions where radioiodine has sufficiently contaminatated the environment. Iodine-131 is used for unsealed source radiotherapy in nuclear medicine to treat several conditions. It can also be detected by gamma cameras for diagnostic imaging, however it is rarely administered for diagnostic purposes only, imaging will normally be done following a therapeutic dose. Use of the I as iodide salt exploits the mechanism of absorption of iodine by the normal cells of the thyroid gland. Major uses of I include the treatment of thyrotoxicosis (hyperthyroidism) due to Graves' disease, and sometimes hyperactive thyroid nodules (abnormally active thyroid tissue that is
Iodine 1% of a sample of gaseous iodine at atmospheric pressure is dissociated into iodine atoms at 575 °C. Temperatures greater than 750 °C are required for fluorine, chlorine, and bromine to dissociate to a similar extent. Most bonds to iodine are weaker than the analogous bonds to the lighter halogens. Gaseous iodine is composed of I molecules with an I–I bond length of 266.6 pm. The I–I bond is one of the longest single bonds known. It is even longer (271.5 pm) in solid orthorhombic crystalline iodine, which has the same crystal structure as chlorine and bromine. (The record is