yttrium (ĭtˈrēəm) [key] [for Ytterby, a town in Sweden], metallic chemical element; symbol Y; at. no. 39; at. wt. 88.90585; m.p. about 1,522°C; b.p. 3,338°C; sp. gr. about 4.45; valence +3. Yttrium is a highly crystalline iron-gray metal. Usually considered a rare-earth metal, it is found above lanthanum in Group 3 of the periodic table. Yttrium is fairly stable in air but oxidizes readily when heated. It reacts with water and mineral acids. The largest use of the element is as its oxide yttria, Y2O3, which is used in making red phosphors for color television picture tubes; it also has other uses. Yttrium metal has found some use alloyed in small amounts with other metals. Yttrium is not found uncombined in nature, but occurs in many minerals, e.g., gadolinite, euxenite, and xenotime. It is recovered commercially from monazite and bastnasite. In 1794, Johan Gadolin isolated impure yttria from the mineral gadolinite. In 1843, C. G. Mosander isolated pure yttria as well as two impure fractions that he called erbia and terbia. The metal was first isolated in 1828 by Friedrich Wöhler.