September 27, 2012, 2:29 pm
caption Albert Einstein





Einsteinium (pronounced ine-STINE-i-em) is a metallic man-made element. On the periodic table, it is represented by the symbol Es and atomic number 99. Einsteinium is the seventh transuranic element, and an actinide. The actinides are the elements found in the last row of the periodic table, having atomic numbers between 89 and 103, and a transuranic element is one that has a higher atomic number than uranium, and is man-made and not found in nature. It was named in honor of Albert Einstein.


Though only small amounts have been made, einsteinium has been determined to be silver-colored. According to tracer studies conducted by Los Alamos National Laboratory using the isotope 253Es, this element has chemical properties typical of a heavy trivalent actinide element. All isotopes of einsteinium are radioactive, and are considered to be potentially toxic.


Einsteinium does not occur naturally in any measurable quantities. The modern process of creating the element starts with the irradiation of 239Pu (plutonium) in a nuclear reactor for several years. The resulting 242Pu isotope (in the form of the compound plutonium (IV) oxide) is mixed with aluminum and formed into pellets. The pellets then undergo extensive and successive nuclear reactions resulting  in a mixture of californium and einsteinium, which can then be separated.


Previous Element: Californium

Next Element: Fermium


Physical Properties
Color ---
Phase at Room Temp. ---
Density (g/cm3) ---
Hardness (Mohs) ---
Melting Point (K) 1133.2
Boiling Point (K) ---
Heat of Fusion (kJ/mol) ---
Heat of Vaporization (kJ/mol) ---
Heat of Atomization (kJ/mol) ---
Thermal Conductivity (J/m sec K) ---
Electrical Conductivity (1/mohm cm) ---
Source Synthetic
Atomic Properties
Electron Configuration [Rn]7s25f11
Number of Isotopes 20 (0 natural)
Electron Affinity (kJ/mol) ---
First Ionization Energy (kJ/mol) 619
Second Ionization Energy (kJ/mol) ---
Third Ionization Energy (kJ/mol) ---
Electronegativity 1.3
Polarizability (Å3) 19.7
Atomic Weight 252.1
Atomic Volume (cm3/mol) ---
Ionic Radius2- (pm) ---
Ionic Radius1- (pm) ---
Atomic Radius (pm) 186
Ionic Radius1+ (pm) ---
Ionic Radius2+ (pm) ---
Ionic Radius3+ (pm) ---
Common Oxidation Numbers +3
Other Oxid. Numbers +2
In Earth's Crust (mg/kg) ---
In Earth's Ocean (mg/L) ---
In Human Body (%) ---
Regulatory / Health
CAS Number 7429-92-7
OSHA Permissible Exposure Limit (PEL) No limits
OSHA PEL Vacated 1989 No limits
NIOSH Recommended Exposure Limit (REL) No limits
Mineral Information Institute
Jefferson Accelerator Laboratory



In addition to its role in basic scientific research in which einsteinium is used to produce other elements, such as mendelevium, this man-made element has no known uses. Only a few compounds of einsteinium have ever been discovered, and none of them have any commercial uses or biological roles. In large amounts, the production of einsteinium could pose a radiation threat.


Einsteinium was first identified in December 1952 by Albert Ghiorso along with co-workers at the University of California, Berkeley. He was examining debris from the first hydrogen bomb test of November 1952. He discovered the isotope 253Es with a half-life of 20.47 days, which was made by the neutron capture of 15 neutrons with 238U (uranium), which then went through 7 beta decays. These findings were kept secret until 1955 because at the time information about atomic tests was restricted.

Isotopes of einsteinium were produced shortly afterward at the University of California Radiation Laboratory by bombarding 238U with 14N (nitrogen) ions, and later by the intense bombardment of neutrons of 239Pu in the Materials Testing Reactor.

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


Nineteen radioisotopes of einsteinium have been characterized, with the most stable being:


471.7 days


275.7 days


39.8 days


20.47 days


7.7 days

All of the remaining isotopes are all also radioactive and have half-lives that are less than 40 hours, with the majority of these having half-lives that are less than 30 minutes. This element also has four isotopes that decay by more than one path, and therefore have more than one half-life.

Known Compounds

The following is a list of all known compounds of einsteinium:

  • 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

Further Reading

  • Einsteinium – National Research Council Canada. Retrieved 9/22/2009
  • Einsteinium – Los Alamos National Laboratory. Retrieved 10/7/2009
  • It’s Elemental – The Element Einsteinium. Retrieved 10/7/2009
  • Albert Ghiorso. Einsteinium and Fermium. Chemical and Engineering News. 2003. Retrieved 9/28/2009
  • National Nuclear Data Center. NuDat 2.5. 2009. Retrieved 9/28/200
  • David L. Heiserman. Exploring Chemical Elements and their Compounds: A guided tour of the Periodic Table. TAB Books, USA. 1992. Pp 349-350
  • Albert Stwertka. A Guide to the Elements. Second Edition. Oxford University Press, New York, New York. 2002. Pp 214
  • The New Encyclopedia Britannica. 15th Edition. 2007. Volume 4 pp 403

Note: This article uses material from the Wikipedia article Einsteinium that was accessed on August 25, 2009. The Author(s) and Topic Editor(s) associated with this article may have significantly modified the content derived from Wikipedia with original content or with content drawn from other sources. All content from Wikipedia has been reviewed and approved by those Author(s) and Topic Editor(s), and is subject to the same peer review process as other content in the EoE. The current version of the Wikipedia article may differ from the version that existed on the date of access. This article is licensed under the GNU Free Documentation License 1.2. See the EoE’s Policy on the Use of Content from Wikipedia for more information.



Coon, M. (2012). Einsteinium. Retrieved from http://www.eoearth.org/view/article/152381


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