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(both: lo͞otē`shēəm), metallic chemical element; symbol Lu; atomic number 71; at. wt. 174.9668; m.p. about 1,663°C;; b.p. about 3,395°C;; sp. gr. 9.835 at 25°C;; valence +3. Lutetium is a silver-white metal that is relatively stable in air. One of the rare-earth metalsrare-earth metals,
in chemistry, group of metals including those of the lanthanide series and actinide series and usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, which is not found in nature, is not usually considered a rare-earth metal.
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, it is the last member of the lanthanide serieslanthanide series,
a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series.
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 in Group 3 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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. The metal may be prepared by reduction of the chloride or fluoride with an alkali or alkaline earth metal. Rare and expensive, it has few commercial uses. The chief commercial source of lutetium is the mineral monazitemonazite
, yellow to reddish-brown natural phosphate of the rare earths, mainly the cerium and lanthanum metals, usually with some thorium. Yttrium, calcium, iron, and silica are frequently present.
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, which contains lutetium in a concentration of about three parts per hundred thousand. A process for separating lutecia (lutetium oxide, a rare earth) from ytterbia was described in 1907 by Georges Urbain, a French chemist, who is credited with the discovery of the element. It was discovered independently in 1908 by Carl Auer von Welsbach, an Austrian chemist, who called the element cassiopeium.


A chemical element, symbol Lu, atomic number 71, atomic weight 174.967; a very rare metal and the heaviest member of the rare-earth group.


, lutecium
a silvery-white metallic element of the lanthanide series, occurring in monazite and used as a catalyst in cracking, alkylation, and polymerization. Symbol: Lu; atomic no.: 71; atomic wt.: 174.967; valency: 3; relative density: 9.841; melting pt.: 1663?C; boiling pt.: 3402?C