Iodine

Iodine is a chemical element, having the chemical symbol I.

Iodine 126.90447(3)   I 53 [Kr] 4d10 5s2 5p5 [ ? ] Halogen:

Its atomic number (the number of protons) is 53. It has a Standard Atomic Weight of 126.90447(3), and is typically found as a solid in its elemental form.

Iodine is considered to be a member of the "Halogen" class of elements, has a boiling point of 184.4 °C , and a melting point of 113.7 °C .

Iodine is specified as a List I chemical by the US Drug Enforcement Administration and is considered to have high risk of diversion to illicit drug manufacturing.

Radioactive iodine-131

¹³¹I is a radioactive isotope of iodine used to treat certain cancers and may be acidentally released by nuclear energy facilities in times of disaster. 131I can be produced in one of two ways: 1) by nuclear fusion for medical uses, or 2) as a by-product of nuclear fission in nuclear energy facilities. ¹³¹I has a half-life of only 8.06 days, so environmental spills are of much less concern that similar spills of other radioactive elements such as cesium or uranium. Thus, a spill of ¹³¹I one thousand times the normal background would decay back to normal levels in about 81 days. The iodine-131 atom undergoes beta-decay and emits gamma radiation in the nuclear fission process. Because iodine is readily absorbed by the thryroid gland, which uses it to produce thyroid hormones, ingestion of radioactive iodine can lead to thyroid pathology, including thyroid cancer.

Ingestion

Like bromine, iodine is readily sublimed, going from the solid state directly to the gaseous state,(skipping the liquid state) so exposure to the solid form can still lead to inhalation of the chemical. Being a halogen, it also readily forms many salts which are readily soluble, so the molecular form is quickly converted into various salts upon reaction with most environments. Dairy animals exposed to any form of radioactive iodine can thus lead to ingestion by humans.