Science / Periodic Table of Elements / Dysprosium (Dy): Atomic number: 66, Atomic mass: 162.50 g.mol -1, Electronegativity: 1.2, Density: 8.6 g.cm-3 at 20°C, Melting point: 1412 °C, Boiling point: 2562 °C, Vanderwaals radius: unknown, Ionic radius: unknown, Isotopes: 12, Electronic shell: [ Xe ] 4f10 6s2, Energy of first ionisation: 571.2 kJ.mol -1, Energy of second ionisation: 1124 kJ.mol -1, Standard potential: - 2.35 V, Discovered by: Paul Emile Lecoq de Boisbaudran in 1886. Dysprosium is a lustrous, very soft, silvery metal. It is stable in air at room temperature even if it is slowly oxydized by oxygen. It reacts with cold water and rapidly dissolves in acids. It forms several brightly coloured salts. Dysprosium's characteristics can be strongly affected by the presence of impurities. Applications: Dysprosium is used in nuclear reactors as a cermet, a composite material made of ceramic and sintered metal, to make laser materials, nuclear reactor control rods, as sources of infrared radiation for studying chemical reactions. Another use in the field of radioactivity is in dosimeters for monitoring exposure to ionizing radiation. Dysprosium in the environment: Dysprosium is one of the more abundant lanthanide elements and is more than twice as abundant as tin. Dysprosium is never encountered as the free element, but is found in many minerals. The most important ores are monazite and bastnasite. World production in around 100 tonnes per year.