ELEMENT: EINSTEINIUM

EINSTEINIUM

Atomic Number:	99
Atomic Symbol:	Es
Atomic Weight:	252
Electron Configuration:	[Rn]7s²5f¹¹
Total Isotopes	30
Total Isomers	11
Radioactive Isotopes	19
Stable Isotopes	0

X-Ray Energies
Kα	117.7
Kβ	132.8
LL	13.42
Lα	16.01
Mz	3.07
Mα	3.83

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View Isotopic & Isomeric Data

History

(Albert Einstein) Einsteinium, the seventh transuranic 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 20-day 253Es isotope was produced.

Albert Einstein In 1961, enough einsteinium was produced to separate a macroscopic amount of 253Es. This sample weighted about 0.01Mg and was measured using a special magnetic-type balance. 253Es so produced was used to produce mendelevium (Element 101).

About 3Mg of einsteinium has been produced at Oak Ridge National Laboratories by

irridiating kilogram quantities of 239Pu in a reactor for several years to produce 242Pu,
fabricating the 242Pu into pellets of plutonium oxide and aluminum powder,
loading the pellets into target rods for an initial 1-year irradiation at the Savannah River Plant, and
irradiating the targets for another 4 months in a HFIR (High Flux Isotopic Reactor).

The targets were then removed for chemical separation of the einsteinium from californium.

Isotopes

Fourteen isotopes of einsteinium are now recognized. 254Es has the longest half-life (275 days).

Properties

Tracer studies using 253Es show that einsteinium has chemical properties typical of a heavy trivalent, actinide element.

Sources: Los Alamos National Laboratory; CRC Handbook of Chemistry and Physics; American Chemical Society


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