Chemical Fact Sheet


Chemical Abstract Number (CAS #) 7429-94-4
Analytical Methods 200.8 - 6020
Atomic Symbol Es

Synopsis from the CRC Handbook of Chemistry and Physics 92nd Edition 2011-2013

Einsteinium — (Albert Einstein [1879–1955]), Es; at. wt. (252); m.p. 860 °C (est.); at. no. 99. Einsteinium, the seventh tran- The Elements 4-11 suranic element of the actinide series to be discovered, was identified by Ghiorso and co-workers at Berkeley in December 1952 in debris from the first large thermonuclear explosion, which took place in the Pacific in November 1952. The isotope produced was the 20-day 253Es isotope. In 1961, a sufficient amount of einsteinium was produced to permit separation of a macroscopic amount of 253Es. This sample weighed about 0.01 μg. A special magnetic-type balance was used in making this determination. 253Es so produced was used to produce mendelevium. About 3 μg of einsteinium has been produced at Oak Ridge National Laboratories by irradiating for several years kilogram quantities of 239Pu in a reactor to produce 242Pu. This was then fabricated into pellets of plutonium oxide and aluminum powder, and loaded into target rods for an initial 1-year irradiation at the Savannah River Plant, followed by irradiation in a HFIR (High Flux Isotopic Reactor). After 4 months in the HFIR the targets were removed for chemical separation of the einsteinium from californium. Nineteen isotopes and isomers of einsteinium are now recognized. 254Es has the longest half-life (276 days). Tracer studies using 253Es show that einsteinium has chemical properties typical of a heavy trivalent, actinide element. Einsteinium is extremely radioactive. Great care must be taken when handling it.

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