Promethium - chemistry.

Promethium - chemistry. Promethium, symbol Pm, radioactive metallic element with an atomic number of 61. Promethium is one of the rare earth elements in the lanthanide series of the periodic table (see Periodic Law). Promethium does not occur naturally on Earth. The fission of uranium is known to produce several radioactive isotopes with atomic number 61. These isotopes were investigated and isolated in 1945 by scientists at the nuclear-research laboratory at Oak Ridge, Tennessee; among them were the American chemists Charles DuBois Coryell, Jacob A. Marinsky, and Lawrence E. Glendenin. They proposed the be named promethium, after the titan Prometheus who stole fire from the gods in Greek mythology. Isotopes with mass numbers from 128 to 163 have been investigated. The most stable isotope of promethium, which has a mass number of 145, has a halflife of 17.7 years; visible amounts of this isotope have been prepared. The metal has been used in atomic batteries and as a beta-particle source in thickness gauges. Promethium melts at about 1042°C (about 1908°F), boils at about 3000°C (about 5432°F), and has a specific gravity of 7.26. See also Beta Particle; Radioactivity. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.