YTTERBIUM

(Yb), chemical element, rare-earth metal of transition Group IIIb of the periodic table, a low-melting-point, divalent rare earth with little commercial use. The first concentrate of ytterbium was obtained (1878) by Jean-Charles-Galinard de Marignac and named by him for the town of Ytterby, Sweden, where the first rare-earth mineral was found. Georges Urbain and Carl Auer von Welsbach independently demonstrated (190708) that Marignac's earth was composed of two oxides, which Urbain called neoytterbia and lutetia. The metals are now known as ytterbium and lutetium. Ytterbium is among the less-abundant rare earths. It occurs in minute amounts in many rare-earth minerals such as xenotime and euxenite and is found in the products of nuclear fission as well. Natural ytterbium consists of seven stable isotopes: ytterbium-168 (0.135 percent), ytterbium-170 (3.03 percent), ytterbium-171 (14.31 percent), ytterbium-172 (21.82 percent), ytterbium-173 (16.13 percent), ytterbium-174 (31.84 percent), and ytterbium-176 (12.73 percent). Ytterbium may be separated from the other rare-earth elements by ion-exchange techniques. The elemental metal is prepared by the thermoreduction of its oxide, Yb2O3, with lanthanum metal. A divalent compound was first prepared (1929) by W.K. Klemm and W. Schuth, who reduced ytterbium(III) chloride, YbCl3, to ytterbium(II) chloride, YbCl2, with hydrogen. The divalent ion, Yb2+, has also been produced by electrolytic reduction or treatment of a trivalent salt with sodium amalgam. The element forms a series of pale-green divalent salts such as ytterbium(II) sulfate, bromide, hydroxide, and carbonate. The pale-green ytterbium ion Yb2+ is unstable in aqueous solution and reduces water readily, liberating hydrogen; it is less stable than the divalent europium ion Eu2+ and more stable than the divalent samarium ion Sm2+. In its predominant trivalent state, ytterbium forms a series of white salts such as ytterbium(III) oxide, sulfate, and nitrate. The relatively soft, silvery-white metal is most conveniently prepared by thermoreduction of the oxide with lanthanum metal followed by distillation of the comparatively volatile ytterbium metal. Elemental ytterbium is oxidized slowly by air at room temperature; and it reacts with water, liberating hydrogen. atomic number 70 atomic weight 173.04 melting point 824 C boiling point 1,193C specific gravity 6.972 (25 C) valence 2, 3 electronic config. 2-8-18-32-8-2 or (Xe)4f 145d06s2