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- DictionaryI·o·dine/ˈīəˌdīn/
noun
- 1. the chemical element of atomic number 53, a nonmetallic element forming black crystals and a violet vapor.
Iodine is a nonmetallic halogen element that is essential for thyroid function and has many uses in medicine, chemistry, and photography. Learn about its history, properties, examples, and related words from Merriam-Webster.
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Iodine is a chemical element that is found in sea water and used in medicine, photography, and as a dye. Learn more about its properties, uses, and examples from the Cambridge Dictionary.
Iodine is a chemical element with symbol I and atomic number 53, the heaviest of the stable halogens. It exists as a non-metallic solid, liquid or gas, and has various oxidation states and applications in medicine, industry and science.
Iodine is a nonmetallic halogen element that sublimes to a violet vapor and is used in medicine and photography. Learn about its properties, history, origin, and examples of iodine in sentences.
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- History
- Occurrence and distribution
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iodine (I), chemical element, a member of the halogen elements, or Group 17 (Group VIIa) of the periodic table.
In 1811 the French chemist Bernard Courtois obtained a violet vapour by heating seaweed ashes with sulfuric acid as a by-product of the manufacture of saltpetre. This vapour condensed to a black crystalline substance, which he called “substance X.” In 1813 British chemist Sir Humphry Davy, who was passing through Paris on his way to Italy, recogniz...
Iodine is never found in nature uncombined, and it is not concentrated sufficiently to form independent minerals. It is present in seawater, but sparingly, as the iodide ion, I−, to the extent of approximately 50 mg per metric ton (0.0016 ounce per ton) of seawater. It is also formed in seaweeds, oysters, and cod livers. Sodium iodate (NaIO3) is contained in crude Chile saltpetre (sodium nitrate, NaNO3). The human body contains iodine in the compound thyroxine, which is produced in the thyroid gland.
The only naturally occurring isotope of iodine is stable iodine-127. An exceptionally useful radioactive isotope is iodine-131, which has a half-life of eight days. It is employed in medicine to monitor thyroid gland functioning, to treat goitre and thyroid cancer, and to locate tumours of the brain and of the liver. It is also used in investigations to trace the course of compounds in metabolism. Several iodine compounds are used as contrast mediums in diagnostic radiology. In aqueous solution even minute amounts of iodine in the presence of starch produce a blue-black colour.
Britannica Quiz
Periodic Table of the Elements
Iodine is a violet-colored halogen element that is never found in nature uncombined. It is essential for thyroid function and has many applications in medicine, radiology, and industry.
Iodine is a trace element essential for thyroid hormone synthesis and metabolic regulation. Learn about iodine intake recommendations, sources, deficiency, health effects, and interactions with medications.
Iodine is a mineral that helps make thyroid hormones that regulate metabolism and growth. Learn about the recommended amounts, food sources, signs of deficiency and toxicity, and related references for iodine.
