(yʊrō'pēӘm) [from Europe], metallic chemical element; symbol Eu; at. no. 63; at. wt. 151.964; m.p. about 820 degrees Celsius; b.p. about 1,600 degrees Celsius; sp. gr. 5.25 at 25 degrees Celsius; valence +2 or +3. Europium is a ductile silvery-white metal; it is both rare and expensive. It is a member of Group 3 of the periodic table. Its oxides are found in minerals with the other rare earths. Europium has been identified in the sun and some stars by spectroscopy. Its physical properties are like those of the other members of the lanthanide series, but many of its chemical properties are more like those of calcium. The most reactive of the rare-earth metals, it tarnishes quickly in air at room temperature and ignites and burns above 150 degrees Celsius. It reacts readily with water. Twenty-one isotopes of europium are known, most of them unstable. Since it is a good neutron absorber, europium metal is used in nuclear reactor control rods. Europium oxide, a pinkish powder, is used to activate red phosphors in the manufacture of color television picture tubes. The discovery of europium is credited to Eugène Demarcay, who isolated fairly pure europium oxide in 1901.
Europium is the most reactive of the lanthanides, the so-called rare earth metals, and one of the rarest ( atomic number =63; relative atomic...
(tûr'bēӘm) [from Ytterby, a village in Sweden], metallic chemical element; symbol Tb; at. no. 65; at. wt. 158.92535; m.p. 1,356 degrees Celsius; b.p
(dĭsprō'zēӘm) [Gr.,=hard to get at], metallic chemical element; symbol Dy; at. no. 66; at. wt. 162.500; m.p. 1,412 degrees Celsius; b.p. 2,562 degre