Yttrium

Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in combination with lanthanide elements in rare-earth minerals and is never found in nature as a free element. 89Y is the only stable isotope and the only isotope found in the Earth's crust. The most important present-day use of yttrium is as a component of phosphors, especially those used in LEDs. Historically, it was once widely used in the red phosphors in television set cathode ray tube displays. Yttrium is also used in the production of electrodes, electrolytes, electronic filters, lasers, superconductors, various medical applications, and tracing various materials to enhance their properties. Yttrium has no known biological role. Exposure to yttrium compounds can cause lung disease in humans. The element is named after ytterbite, a mineral first identified in 1787 by the chemist Carl Axel Arrhenius. He named the mineral after the village of Ytterby, in Sweden, where it had been discovered. When one of the chemicals in ytterbite was later found to be a previously unidentified element, the element was then named yttrium after the mineral. Yttrium is a soft, silver-metallic, lustrous and highly crystalline transition metal in group 3. As expected by periodic trends, it is less electronegative than its predecessor in the group, scandium, and less electronegative than the next member of period 5, zirconium. However, due to the lanthanide contraction, it is also less electronegative than its successor in the group, lutetium. Yttrium is the first d-block element in the fifth period. The pure element is relatively stable in air in bulk form, due to passivation of a protective oxide (Y2O3) film that forms on the surface. This film can reach a thickness of 10 μm when yttrium is heated to 750 °C in water vapor. When finely divided, however, yttrium is very unstable in air; shavings or turnings of the metal can ignite in air at temperatures exceeding 400 °C.