einsteinium

einsteinium

a metallic transuranic element artificially produced from plutonium. Symbol: Es; atomic no.: 99; half-life of most stable isotope, ²⁵²Es: 276 days

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

einsteinium

[īn′stīn·ē·əm]

(chemistry)

Synthetic radioactive element, symbol Es, atomic number 99; discovered in debris of 1952 hydrogen bomb explosion; now made in cyclotrons.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Einsteinium

 

Es, a synthetic radioactive chemical element, a member of the actinide series; atomic number, 99. Einsteinium has no stable isotopes; it has known isotopes with mass numbers 243 through 256.

The seventh transuranium element to be discovered, einsteinium was identified by A. Ghiorso and others in December 1952 in the debris from a thermonuclear explosion in the course of work involving members of the University of California Radiation Laboratory, the Argonne National Laboratory, and the Los Alamos Scientific Laboratory (USA). The isotope produced was ²⁵³Es, with a half-life of 20.5 days, originating from the beta decay of ²⁵³U and daughters; the ²³⁵U was formed by the essentially successive capture of 15 neutrons by ²³⁸U.

Einsteinium can be investigated with macroscopic quantities using the isotopes ²⁵³Es (half-life 20.5 days), ³⁵⁴Es (half-life 276 days), and ²⁵⁵Es (half-life 38.3 days), whose production by the irradiation of lighter elements is severely limited because of the required long sequence of neutron capture reactions over long periods of time in high-neutron-flux reactors. Most of the investigations have used the short-lived ²⁵³Es because of its greater availability, but the use of ²⁵⁴Es will increase as it becomes more available. In any case, the investigation of einsteinium is very difficult because of the high specific radioactivity and small available quantities of the isotopes.

Einsteinium metal, which is quite volatile, can be prepared by the reduction of EsF₃ with lithium and has a face-centered cubic crystal structure. The melting point is 860±30°C.

Einsteinium exists in normal aqueous solution in most stable form as Es ⁺³ (green), although Es ⁺² can be produced under strong reducing conditions. The Es⁺³/Es⁺² reduction potential is estimated to be − 1.24 ± 0.2 volt on the scale in which the hydrogen ion-hydrogen potential is 0.0 volt.

Numerous solid compounds, such as Es₂O₃, EsCl₃, EsOCl, EsBr₂, EsBr₃, Esl₂, and Esl₃, have been synthesized and studied.

The electron structure of the gaseous element is 5f¹¹7s² (beyond the radon structure).

REFERENCE

Seaborg, G. T. lskusstvennye transuranovye elementy. Moscow, 1965. (Translated from English.)

G. T. SEABORG

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.