tailieunhanh - Encyclopedia of Global Resources part 23

Encyclopedia of Global Resources part 23 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 190 Cesium Global Resources Web Site University of Illinois Urbana-Champaign Department of Materials Science and Engineering Ceramics http ceramics See also Abrasives Clays Glass Mica Quartz Sand and gravel Silicates Silicon. Cesium Category Mineral and other nonliving resources Where Found The element cesium makes up only 7 parts per million of the Earth s crust. Found only in minerals it does not occur in its free state naturally. The leading producers are in southwest Africa the Russian republics Sweden and the island of Elba. In North America it is most often found in ores in South Dakota Maine and Manitoba Canada. Significant reserve bases exist in Namibia and Zimbabwe as well as Canada. Primary Uses Cesium has significant applications in the manufacture of photoelectric cells and vacuum tubes. One of its isotopes cesium 137 is used in radiation therapy. Cesium compounds have also ser ved as antishock agents after administration of arsenic drugs. The International Atomic Energy Agency has also identified cesium 137 as one of the radioactive materials that may be used to make dirty bombs. Technical Definition Cesium abbreviated Cs atomic number 55 belongs to Group I of the periodic table of the elements and is the heaviest of the alkali metals excluding the radioactive francium . It has twenty-two known isotopes with masses ranging from cesium 123 to cesium 144 with an average atomic weight of . The only naturally occurring isotope is cesium 133. Description Distribution and Forms Pure cesium is a silver-white ductile metal that is extremely malleable. Finely divided cesium produces a blue flame and is easily oxidized by burning brightly in humid air it may explode in the presence of water. It has a density of grams per cubic centimeter a melting point of Celsius and a boiling point of 705 Celsius. History Cesium was discovered and detected by spectroscopy in 1860 by the German scientists Robert Bunsen and .