Einsteinium (pronEng|aɪnˈstaɪniəm) is a metallic synthetic element. On the periodic table, it is represented by the symbol Es and atomic number 99. It is the seventh transuranic element, and seventh in the series of Actinides. It was named in honor of Albert Einstein.


Its position on the periodic table indicates that its chemical and physical properties are similar to other metals. Though only small amounts have ever been made, it has been determined to be silver-colored. According to tracer studies conducted at Los Alamos National Laboratory using the isotope 253Es, this element has chemical properties typical of a heavy trivalent, actinide element.

Like all synthetic elements, isotopes of einsteinium are radioactive.


Einsteinium does not occur naturally in any measurable quantities. The modern process of creating the element starts with the irradiation of plutonium-239 in a nuclear reactor for several years. The resulting plutonium-242 isotope (in the form of the compound plutonium(IV) oxide) is mixed with aluminium and formed into pellets. The pellets are then further irradiated for approximately one year in a nuclear reactor. Another four months of irradiation is required in a different reactor. The result is a mixture of californium and einsteinium, which can then be separated. [http://periodic.lanl.gov/elements/99.html Einsteinium - Los Alamos National Laboratory] . Retrieved 2 December 2007.]


Aside from being the byproduct of creating other elements, or a step in the production of other elements, einsteinium has no known uses. [ [http://education.jlab.org/itselemental/ele099.html It's Elemental - The Element Einsteinium] . Retrieved 2 December 2007.]


Einsteinium was first identified in December 1952 by Albert Ghiorso and co-workers at the University of California, Berkeley.cite web| url=http://periodic.lanl.gov/elements/99.html | title=Einsteinium - Los Alamos National Laboratory| access-date=2007-12-07] He was examining debris from the first hydrogen bomb test of November 1952 (see Operation Ivy). [http://www.nrc-cnrc.gc.ca/eng/education/elements/el/es.html Einsteinium - National Research Council Canada] . Retrieved 2 December 2007.] cite web| url = http://pubs.acs.org/cen/80th/einsteiniumfermium.html | title=Einsteinium and Fermium | author = Albert Ghiorso | publisher = Chemical and Engineering News } date = 2003] He discovered the isotope 253Es (half-life 20.5 days) that was made by the neutron capture of 15 neutrons with 238U (which then went through seven beta decays). These findings were kept secret until 1955 due to Cold War tensions.cite journal
title = New Elements Einsteinium and Fermium, Atomic Numbers 99 and 100
author = Ghiorso, A. and Thompson, S. G. and Higgins, G. H. and Seaborg, G. T. and Studier, M. H. and Fields, P. R. and Fried, S. M. and Diamond, H. and Mech, J. F. and Pyle, G. L. and Huizenga, J. R. and Hirsch, A. and Manning, W. M. and Browne, C. I. and Smith, H. L. and Spence, R. W.
journal = Phys. Rev.
volume = 99
doi = 10.1103/PhysRev.99.1048
url = http://prola.aps.org/abstract/PR/v99/i3/p1048_1
pages = 1048–1049
year = 1955

Isotopes of einsteinium were produced shortly afterward at the University of California Radiation Laboratory in a nuclear fusion reaction between 14N and 238Ucite journal
journal = Physical Review
volume = 93
date = 1954
title = Reactions of U-238 with Cyclotron-Produced Nitrogen Ions
author = Ghiorso, Albert and Rossi, G. Bernard and Harvey, Bernard G. and Thompson, Stanley G.
doi = 10.1103/PhysRev.93.257
pages = 257
] and later by intense neutron irradiation of plutonium in the Materials Testing Reactor.cite journal
journal = Physical Review
volume = 93
date = 1954
title = Transcurium Isotopes Produced in the Neutron Irradiation of Plutonium
author = Thompson, S. G. and Ghiorso, A. and Harvey, B. G. and Choppin, G. R.
doi = 10.1103/PhysRev.93.908
pages = 908

In 1961, enough einsteinium was synthesized to prepare a microscopic amount of 253Es. This sample weighed about 0.01 mg and was measured using a special balance. The material produced was used to produce mendelevium. Further einsteinium has been produced at the Oak Ridge National Laboratory's High Flux Isotope Reactor in Tennessee by bombarding 239Pu with neutrons. Around 3 milligrams were created over a four year program of irradiation and then chemical separation from a starting 1 kg of plutonium isotope.


Nineteen radioisotopes of einsteinium have been characterized, [ [http://ie.lbl.gov/toi/listnuc.asp?sql=&Z=99 Table of Isotopes decay data - LBNL Isotopes Project - LUNDS Universitet] . Retrieved 25 November 2007.] with the most stable being 252Es with a half-life of 471.7 days, 254Es with a half-life of 275.7 days, 255Es with a half-life of 39.8 days, and 253Es with a half-life of 20.47 days. All of the remaining radioactive isotopes have half-lives that are less than 40 hours, and the majority of these have half-lives that are less than 30 minutes. This element also has three meta states, with the most stable being 254mEs (t½ 39.3 hours). The isotopes of einsteinium range in atomic mass from 240.069 u (240Es) to 258.100 u (258Es). The longest-lived isotope is 252Es.

Known compounds

The following is a list of all known compounds of einsteinium: [ [http://www.webelements.com/webelements/elements/text/Es/comp.html Chemistry : Periodic Table : einsteinium : compounds information - WebElements] . Retrieved 2 December 2007.]

* EsBr2 einsteinium(II) bromide
* EsBr3 einsteinium(III) bromide
* EsCl2 einsteinium(II) chloride
* EsCl3 einsteinium(III) chloride
* EsF3 einsteinium(III) fluoride
* EsI2 einsteinium(II) iodide
* EsI3 einsteinium(III) iodide
* Es2O3 einsteinium(III) oxide


* "Guide to the Elements - Revised Edition", Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1

External links

* [http://periodic.lanl.gov/elements/99.html Los Alamos National Laboratory - Einsteinium]
* [http://education.jlab.org/itselemental/ele099.html It's Elemental - The Element Einsteinium]
* [http://www.webelements.com/webelements/elements/text/Es/index.html WebElements.com - Einsteinium]
* [http://pubs.acs.org/cen/80th/einsteiniumfermium.html Albert Ghiorso about the discovery]
* [http://periodic.lanl.gov/elements/99.html Einsteinium - Los Alamos National Laboratory]

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  • einsteinium — Symbol: Es Atomic number: 99 Atomic weight: (254) Appearance is unknown, however it is most probably metallic and silver or gray in color. Radioactive metallic transuranic element belonging to the actinoids. Es 254 has the longest half life of… …   Elements of periodic system

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  • einsteinium — /uyn stuy nee euhm/, n. Chem., Physics. a transuranic element. Symbol: Es; at. no.: 99. [1950 55; named after Albert EINSTEIN; see IUM] * * * ▪ chemical element  (Es), synthetic chemical element of the actinoid series of the periodic table,… …   Universalium

  • einsteinium — Es Es n. the chemical symbol for {einsteinium}, a transuranic element with atomic number 99. The atomic weight of the longest lived isotope, with a half life of 276 days, is 254. The first isotope discovered, having atomic weight 253 and a half… …   The Collaborative International Dictionary of English

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