From New World Encyclopedia

99 californiumeinsteiniumfermium


periodic table
Name, Symbol, Number einsteinium, Es, 99
Chemical series actinides
Group, Period, Block n/a, 7, f
Appearance unknown, probably silvery
white or metallic gray
Atomic mass (252) g/mol
Electron configuration [Rn] 5f11 7s2
Electrons per shell 2, 8, 18, 32, 29, 8, 2
Physical properties
Phase solid
Density (near r.t.) 8.84 g/cm³
Melting point 1133 K
(860 °C, 1580 °F)
Atomic properties
Oxidation states 2, 3, 4
Electronegativity 1.3 (Pauling scale)
Ionization energies 1st: 619 kJ/mol
Magnetic ordering no data
CAS registry number 7429-92-7
Notable isotopes
Main article: Isotopes of einsteinium
iso NA half-life DM DE (MeV) DP
252Es syn 471.7 d α 6.760 248Bk
ε 1.260 252Cf
β- 0.480 252Fm
253Es syn 20.47 d SF - -
α 6.739 249Bk
254Es syn 275.7 d ε 0.654 254Cf
β- 1.090 254Fm
α 6.628 250Bk
255Es syn 39.8 d β- 0.288 255Fm
α 6.436 251Bk
SF - -

Einsteinium (chemical symbol Es, atomic number 99) is a synthetic element in the periodic table. A metallic, highly radioactive, transuranic element[1] (seventh in the series) in the actinides, einsteinium is produced by bombarding plutonium with neutrons and was discovered in the debris of the first hydrogen bomb test. It is of interest mainly for scientific research, and practical applications of the element have yet to be developed.


Einsteinium was named after Albert Einstein. It was first identified in December 1952 by Albert Ghiorso at the University of California, Berkeley and another team headed by G.R. Choppin at Los Alamos National Laboratory. Both were examining debris from the first hydrogen bomb test of November 1952 (see Operation Ivy). They discovered the isotope 253Es (half-life 20.5 days) that was made by the nuclear fusion of 15 neutrons with 238U (which then went through seven beta decays). These findings were kept secret until 1955 due to Cold War tensions, however.

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 three mg was created over a four year program of irradiation and then chemical separation from a starting one kg of plutonium isotope.

Notable characteristics

Einsteinium is an inner transition metal of the actinide series, located in period seven of the periodic table, between californium and fermium. Tracer studies using the isotope 253Es show that einsteinium has chemical properties typical of a heavy trivalent, actinide element.


19 radioisotopes of einsteinium have been characterized, 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 amu (240Es) to 258.100 amu (258Es).


Known compounds of einsteinium include the following:

  • Fluoride:
    • einsteinium(III) fluoride (EsF3)
  • Chlorides:
    • einsteinium(II) chloride (EsCl2)
    • einsteinium(III) chloride (EsCl3)
  • Bromides:
    • einsteinium(II) bromide (EsBr2)
    • einsteinium(III) bromide (EsBr3)
  • Iodides:
    • einsteinium(II) iodide (EsI2)
    • einsteinium(III) iodide (EsI3)
  • Oxide:
    • einsteinium(III) oxide (Es2O3)

See also


  1. "Transuranic elements" are the chemical elements with atomic numbers greater than that of uranium (atomic number 92).

ISBN links support NWE through referral fees

  • Emsley, John. Nature's Building Blocks: An A–Z Guide to the Elements. Oxford: Oxford Univ. Press, 2003 (original 2001). ISBN 0198503407
  • Greenwood, N.N., and A. Earnshaw. Chemistry of the Elements. Oxford, UK; Burlington, MA: Butterworth-Heinemann, 2nd ed.1998. ISBN 0750633654 Online version Retrieved December 24, 2021.
  • Hampel, Clifford A. The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corp., 1968 ISBN 0442155980
  • Morss, Lester R., Norman M. Edelstein, and Jean Fuger, eds. The Chemistry of the Actinide and Transactinide Elements. 3rd ed. 5 vols. Joseph J. Katz, adapter. Dordrecht: Springer, 2006. ISBN 1402035551
  • Stwertka, Albert. Guide to the Elements. Rev. ed. Oxford: Oxford University Press, 1998. ISBN 0-19-508083-1

External links

All links retrieved September 19, 2017.


New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

The history of this article since it was imported to New World Encyclopedia:

Note: Some restrictions may apply to use of individual images which are separately licensed.