3/1/2023 0 Comments Ir periodic table chemistry![]() ![]() The Earth's core is rich in iridium, and Piton de la Fournaise on Réunion, for example, is still releasing iridium today. McLean and others argue that the iridium may have been of volcanic origin instead. This theory is widely accepted by scientists. They attributed this iridium to an asteroid or comet impact, and theorized that this impact was responsible for the demise of the dinosaurs. In 1980, a team led by Luis Alvarez found a thin stratum of iridium-rich clay near what is now Yucatán Peninsula. Iridium has also been linked to evidence for what is known as the "Cretaceous-Tertiary extinction event" ("KT event") of 65 million years ago, at the temporal boundary between the Cretaceous and Tertiary eras. In 1960, the meter bar was replaced as the definition of the fundamental unit of length (see krypton), but the kilogram prototype is still the international standard of mass. The element was named after the Latin word iris, meaning rainbow, because many of its salts are strongly colored.Īn alloy of 90 percent platinum and 10 percent iridium was used in 1889 to construct the standard meter bar and kilogram mass, kept by the Bureau International des Poids et Mesures (International Bureau of Weights and Measures) near Paris. Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804. In the summer of 1803, Tennant identified two new elements- osmium and iridium. Wollaston focused on analyzing the soluble portion and discovered palladium (in 1802) and rhodium (in 1804), while Tennant examined the insoluble residue. A large amount of insoluble black powder remained as a byproduct of this operation. They were looking for a way to purify platinum by dissolving native platinum ore in aqua regia (a mixture of concentrated hydrochloric and nitric acids). ![]() Iridium was discovered in 1803 by Smithson Tennant, while working with William Hyde Wollaston in London, England. Iridium is recovered commercially as a byproduct from nickel mining and processing. Naturally occurring iridium alloys include osmiridium and iridiosmium, both of which are mixtures of iridium and osmium. The element is found in nature with platinum and other platinum group metals in alluvial deposits. Also, iridium is relatively common in meteorites. Iridium is rare in the Earth's crust, but it is found at higher concentrations in some volcanic flows, suggesting that the Earth's core is richer in this element. It is a catalyst for certain reactions in organic chemistry, and radioactive iridium may be used in radiation therapy for some types of cancer. It is used in high-temperature apparatuses and electrical contacts, and as a hardening agent for platinum alloys. Researchers have associated it with a meteorite strike that is thought to have caused the demise of dinosaurs. It occurs in natural alloys with platinum or osmium and is notable for being the most corrosion-resistant element known. Iridium (chemical symbol Ir, atomic number 77) is a dense, hard, brittle, silvery-white transition metal of the platinum family. ![]()
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