formerly lutecium (both: lōtē'shēӘm), metallic chemical element; symbol Lu; atomic number 71; at. wt. 174.9668; m.p. about 1,663 degrees Celsius; b.p. about 3,395 degrees Celsius; sp. gr. 9.835 at 25 degrees Celsius; valence +3. Lutetium is a silver-white metal that is relatively stable in air. One of the rare-earth metals, it is the last member of the lanthanide series in Group 3 of the periodic table. 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 monazite, 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.
(ĭtûr'bēӘm) [for Ytterby, a town in Sweden], metallic chemical element; symbol Yb; at. no. 70; at. wt. 173.054; m.p. 819 degrees Celsius; b.p. about
Chemical element in the lanthanide series, chemical symbol Tb, atomic number 65. It was named after the Swedish town of Ytterby, where it was disco
Yellowish metallic element of the lanthanide series, atomic number 60, relative atomic mass 144.24. Its rose-coloured salts are used in colouring gla