Periodic Table -> Iodine


Iodine Details

Iodine Symbol: I

Iodine Atomic Number: 53

Iodine Atomic Weight: 126.904

What is Iodine?

Iodine (atomic number 53, symbol I) is a chemical element with low toxicity, which dissolves easily in chloroform, hexane, and other organic solvents due to its lack of polarity. The color of iodine solutions depends on the solvent and its polarity. Solutions are violet in color in hexane and other non-polar solvents and dark crimson in moderately polar ones. Solutions are brown or orange in strongly polar solvents, for example, ethanol and acetone. When iodine is dissolved in carbon disulphide, carbon tetrachloride, or chloroform, it yields purple-colored solutions. Iodine is slightly soluble in water and gives a yellow solution.

This element is shiny, blue-black, nonmetallic solid, volatizing into a violet-blue gas at room temperature. It has an irritating odor as well. Iodine is less reactive compared to other halogens and forms compounds with different elements. Iodine also exhibits some properties characteristic of metals. It binds to starch, coloring it dark blue.

Iodine was discovered in 1811 by Bernard Courtois who gave samples to Nicolas Clement and Charles Desormes to continue research. At a meeting of the Imperial Institute, Clement and Courtois described the new substance.

Iodine has 37 isotopes but only one of them is stable (127I). The half-life of one of its longest lived radioisotopes, 129I is 15.7 million years. The next longest-lived radioisotope of iodine is iodine-125, but its half-life is only 59 days. This isotope is used in some imaging tests in nuclear medicine, in brachytherapy implanted capsules, and as a gamma-emitting tag.

Iodine has multiple applications as well. It is used for water treatment, as a disinfectant, and as a radiocontrast agent. There are special applications of inorganic iodides. Titanium, zirconium, and hafnium are purified by using the van Arkel Process. Then, the main component of photographic film is silver iodide, while cloud seeding consumes thousands of kilograms of the compound a year. Some disorders of the thyroid gland are treated by using iodine-131, which is a radioactive isotope of the element.

This element is found in seaweeds and seawater as well as in nitrate bearing earth, Chilean saltpeter, brines from sea deposits, and brackish waters from oil wells and salt wells. The reaction between copper sulfate and potassium iodide produces ultrapure iodine.

Iodine is very important for proper nutrition, but handling it requires caution. Lesions are caused by skin contact, and the vapor irritates the mucous membranes and the eyes. In animal biology, the main role of iodine is as a component of the thyroid hormones T3 or triiodothyronine and T4 or thyroxine. These hormones are produced from tyrosineís condensation products and are deposited before the release of thyroglobulin, which is an iodine-containing protein. Iodide is absorbed from the blood by the thyroid gland so that these hormones are released into the blood stream. Another hormone (TSH) regulates these actions, and it is produced by the pituitary. Most multicellular organisms synthesize thyroid hormones and they have an effect on some unicellular organisms as well.

Iodine is the main component of thyroid hormones, which are essential for metabolism, the nervous system, and growth. Iodine shortages are experienced by persons who eat no or little bread. The thyroid glandís function slows down, and it swells up. The intake of large quantities is dangerous and can affect all organs in the body, causing loss of weight and disturbed heartbeats.

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