{"id":96,"date":"2018-10-19T10:39:58","date_gmt":"2018-10-19T10:39:58","guid":{"rendered":"http:\/\/periodic-table.com\/?p=96"},"modified":"2018-11-13T14:27:36","modified_gmt":"2018-11-13T14:27:36","slug":"iodine","status":"publish","type":"post","link":"https:\/\/periodic-table.com\/iodine\/","title":{"rendered":"IODINE"},"content":{"rendered":"

Iodine belongs to halogen group in the periodic table. Iodine is an essential mineral commonly found in sea food. Iodine plays an important role in proper functioning of thyroid hormone in the human body. <\/em><\/strong><\/p>\n

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Discovery and History<\/strong><\/p>\n

During Napoleonic Wars, Bernard Courtois, a French chemist discovered Iodine in 1811, while he was extracting sodium and potassium compounds from seaweed ash. He noticed a cloud of violet gas when sulfuric acid was added to the ash and proposed that a distinct element is present in the ashes. Two years later Joseph Louis Gay-Lussac gave the name \u201ciode\u201d <\/em>to this element, that is the Greek word for \u2018\u2019violet colored\u2019\u2019. Iodized table salt was sold first time in Michigan in 1924 [1].<\/p>\n

Occurrence <\/strong><\/p>\n

Iodine is the 61st<\/sup> most abundant element on Earth. It is a rare element and does not exist in free -state. About 50mg per metric tons of iodine is present in the sea water [2]. Iodine is the least abundant halogens and is present in only 0.46 ppm (parts per million) of earth crust rocks. The mineral Caliche (sedimentary rock), is the main source of iodine. \u00a0Brine (high concentration of iodine in water) is also used for the extraction of iodine and Japan and USA have major deposits of brine. Iodine is also formed in oysters, seaweeds and cod liver. Human body contains iodine in the form of thyroxin produced by the thyroid glands. Iodine is chiefly obtained from sodium iodate (NaIO3<\/sub>) and sodium periodate (NaIO4<\/sub>). Chile and Japan are prime producer of iodine in the world.<\/p>\n

Physical characteristics<\/strong><\/p>\n

Iodine is bluish black, shiny solid and has a pungent odor. It is non -metal but show some metallic properties. Iodine is hardly dissolved in water but gives a yellow color solution. Iodine belongs to group halogens, that are the salt formers. Iodine when dissolved in chloroform gives purple color solution. Melting point and boiling point of iodine are highest as compared to other halogens. Its melting point is 113.70<\/sup>C and boiling point is about 184.30<\/sup>C. Atomic number of iodine is 63 and easily attached with organic compounds. \u00a0Iodine\u2019s atomic weight is 126.90. The density of iodine is very low, about 4.94g\/ml.<\/p>\n

Chemical characteristics<\/strong><\/p>\n

Iodine is reactive element among the halogens. It has lowest ionization energy and is easily oxidized. Iodine has various oxidation states, including +1 (iodides), +3, +5 (iodates) and +7 (periodate). and is more stable than bromine and chlorine. Iodine molecules act as Lewis acid with combined with many Lewis bases. Electron affinity of iodine is also similar to other halogen atoms. The simplest compound of iodine is hydrogen iodide. It is a colorless gas that reacts with oxygen to give water and iodine. Iodine does not react with oxygen or nitrogen. \u00a0Iodine reacts with nonmetals and forms iodides, for example, silver and aluminum are converted into iodides. The iodide ion is a strong reducing agent and gives up electron easily. Iodide solutions are colorless but gives brownish tint due to oxidation. Iodine reacts with zinc and forms zinc iodide. This reaction is very exothermic and produce violet color vapors of iodine.<\/p>\n

Significance and Uses<\/b><\/p>\n