Einsteinium - chemistry.

Einsteinium - chemistry. Einsteinium, symbol Es, artificially created radioactive element with an atomic number of 99. Einsteinium is one of the transuranium elements in the actinide series of the periodic table (see Periodic Law). The element was named in honor of German-born American physicist Albert Einstein. Einsteinium was discovered in 1952 by American chemist Albert Ghiorso and colleagues at the University of California, Berkeley. The scientists discovered the element in the debris produced by a thermonuclear explosion (see Nuclear Weapons). The isotope first identified had an atomic mass of 253 and a half-life of 20 days. Subsequently, the most long-lived of all the known einsteinium isotopes, einsteinium-254, was prepared by irradiating plutonium in a nuclear reactor; however, only small amounts are now being produced (see Radioactivity). Isotopes of einsteinium with mass numbers ranging from 241 to 257 are known. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.