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The rare-earth elements (REE), also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), [1] are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals. Compounds containing rare ...
Rare-earth ore, shown with a United States penny for size comparison. A rare-earth mineral contains one or more rare-earth elements as major metal constituents. Rare-earth minerals are usually found in association with alkaline to peralkaline igneous complexes in pegmatites. This would be associated with alkaline magmas or with carbonatite ...
Praseodymium is not particularly rare, despite it being in the rare-earth metals, making up 9.2 mg/kg of the Earth's crust. [43] Praseodymium's classification as a rare-earth metal comes from its rarity relative to "common earths" such as lime and magnesia, the few known minerals containing it for which extraction is commercially viable, as ...
The term rare-earth element or rare-earth metal is often used to include the stable group 3 elements Sc, Y, and Lu in addition to the 4f elements. [8] All lanthanide elements form trivalent cations, Ln 3+, whose chemistry is largely determined by the ionic radius, which decreases steadily from lanthanum (La) to lutetium (Lu).
Like most other rare earth elements, its usual oxidation state is +3, although some compounds are known with an oxidation state of +2. Lanthanum has no biological role in humans but is used by some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity. Lanthanum usually occurs together with cerium and the ...
Neodymium is fairly common—about as common as cobalt, nickel, or copper—and is widely distributed in the Earth's crust. [10] Most of the world's commercial neodymium is mined in China, as is the case with many other rare-earth metals. Neodymium compounds were first commercially used as glass dyes in 1927 and remain a popular additive.
Four decades ago, a rare earth processing plant on France's Atlantic coast was one of the largest in the world, churning out materials used to make colour televisions, arc lights and camera lenses.
The rare earth element lutetium was independently discovered by three scientists at around the same time in 1907: French scientist Georges Urbain, Austrian Auer von Welsbach, and American Charles James. [18] [9] All three were successful in separating the substance then known as ytterbium into two new fractions.