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

Several isotopes of iodine, including ¹²³I, ¹²⁴I, ¹²⁹I and ¹³¹I are radioactive isotopes of iodine used to treat certain cancers or for medical imaging processes and ¹³¹I 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. In fact, both ¹²⁹I and ¹³¹ are produced by fission reactions of uranium in nuclear energy facilities or by detonation of nuclear weapons. I are produced by the fision of uranium 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. However, ¹²⁹I has a half-life of 15.7 million years. Thus, a spill of ¹³¹I one thousand times the normal background would decay back to normal levels in about 81 days. The ¹²⁹I and ¹³¹I atoms emit beta particles and emit gamma radiation during radioactive decay. 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.