Einsteinium (Es)

• Element Symbol: Es
• Atomic Number: 99
• Atomic Mass: 252
• Group # in Periodic Table: n/a
• Group Name: Actinides
• Period in Periodic Table: 7
• Block of Periodic Table: f-block
• Discovered by: Albert Ghiorso, Torbjørn Sikkeland, Almon E. Larsh, Robert M. Latimer (1952)

Einsteinium is a silvery, highly radioactive element that is part of the actinide series in the periodic table. The actinides, which are metals with atomic numbers between 89 and 103, also include actinium, thorium, uranium, plutonium, curium, berkelium, californium, fermium, and lawrencium. Some actinide elements, such as uranium and thorium, have isotopes that are naturally abundant within minerals in Earth’s crust. Radioactive decay of these natural isotopes produces other actinides, such as actinium. Some actinides are not found in nature and must be produced synthetically. Einsteinium is one of the synthetic actinides. This element was originally produced during a thermonuclear explosion. It can also be produced in a particle accelerator or nuclear reactor.

Einsteinium is a transuranium element. This category of elements includes all those with atomic numbers greater than 92, the atomic number of uranium. Transuranium elements are radioactive and unstable. The transuranium actinides were discovered between 1940 and 1961.

Einsteinium was discovered in 1952 after detonation of the first thermonuclear device (code-named Mike) in the South Pacific. Filter paper containing radioactive material from the nuclear explosion was sent to a team of American physicists at the University of California, Berkeley. This team included Stanley G. Thompson, Gary Higgins, and Albert Ghiorso. First, these scientists chemically separated isotopes from the filter paper, and then they identified alpha particles from a new element with the atomic number 99. The isotope they had discovered had a half-life of around one month.

The Berkeley team joined forces with teams from Los Alamos National Laboratory and Chicago’s Argonne National Laboratory. Further research was done on radiation fallout from coral reefs near the Mike explosion. This research yielded more evidence of element 99 as well as evidence of another new element, one with atomic number 100.

Because the detonation of Mike was classified as top secret, the researchers could not immediately publish their discovery of elements 99 and 100. However, they were able to produce and chemically isolate the two elements after neutron bombardment within the Crocker Laboratory cyclotron in California and the high-flux nuclear reactor in Idaho. This unclassified work paved the way for the declassification of the Mike research. The scientists who had been involved in the discovery of these two new elements could then get credit. They were also entitled to name the elements. Element 99 was named einsteinium, after German physicist Albert Einstein. Element 100 was named fermium, after Italian American physicist Enrico Fermi.

Einsteinium and fermium were two of the many actinide elements to be discovered, at least in part, by researchers at the University of California, Berkeley. Berkeley scientists were involved in the discovery of the actinides with atomic numbers from 93 to 103. Ghiorso, who was head of the teams that discovered einsteinium and fermium, was involved in the discovery of the actinides with atomic numbers from 96 to 103.

The thermonuclear device that created einsteinium and fermium was a result of work started by the Manhattan Project. This project spurred research on radioactive elements in the United States during and after World War II.

Physical Properties

Einsteinium is a silvery metal that is solid in its standard state at 298 kelvins (K). Most properties of einsteinium are unknown, both because it is highly radioactive and volatile and because it can only be produced in small quantities. Einsteinium has a melting point of 860 degrees Celsius (°C). Its density, boiling point, specific heat, and thermal conductivity are unknown. Also unknown are its electrical conductivity, resistivity, and magnetic type.

Chemical Properties

Einsteinium has a face-centered crystal structure that is similar to the structure of the lanthanides europium and ytterbium. The electron affinity of einsteinium is unknown. This element has four valence electrons. Its electronegativity is 1.3. Its ionization energies are 619 and 1158 kilojoules per mole (kJ/mol). Einsteinium has a +3 oxidation states in solid compounds and aqueous solutions. Evidence suggests a +2 oxidation state in gaseous einsteinium and nonaqueous and solid solutions containing einsteinium ions.

Einsteinium has no stable isotopes. It has nineteen known radioactive isotopes. Their mass numbers range from 240 to 258. The first isotope discovered was einsteinium-253, which was produced during the first thermonuclear explosion. This isotope has also been created in nuclear reactors and is produced in the largest quantities for research. Its half-life is 20.5 days. Einsteinium-254 can be produced through neutron bombardment in a high-flux reactor. This isotope has a half-life of 276 days. Einsteinium-255 can also be produced through neutron bombardment. It has a half-life of 39.8 days. Einsteinium-241 has the shortest half-life, at eight seconds. The longest-lived isotope is einsteinium-252, with a half-life of 471.7 days. Einsteinium has an electron configuration of [Rn]5f¹¹7s².

Applications

Einsteinium is not found in nature. Since its original production during a thermonuclear explosion, it has subsequently been produced within particle accelerators and nuclear reactors. The elements uranium, neptunium, americium, californium, and berkelium can all be used as targets in the production of einsteinium. Multiple neutron capture can also produce isotopes of einsteinium. During this process, an element such as curium is bombarded with neutrons within a reactor, and the neutrons are absorbed. The resulting isotopes are then allowed to undergo beta decay until the desired isotope is achieved. Einsteinium can be separated from other reactor products through ion exchange, extraction chromatography, and solvent extraction.

The High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory can produce up to two milligrams of einsteinium-253 every six to twenty-four months. The small amounts of einsteinium produced, its short half-life, and the intense heat and radiation emitted by the isotope all make studying einsteinium difficult.

Einsteinium has few applications. It has primarily been used within particle accelerators or reactors to produce elements with higher atomic numbers, such as fermium or mendelevium. It has also been used to study the damaging effects of radiation.

Einsteinium has been investigated for use in radiation therapy. One proposed method is to bind einsteinium to a biological agent that can then carry the radioactive isotope to a cancerous tumor.

Bibliography

Aldersey-Williams, Hugh. Periodic Tales: A Cultural History of the Elements, from Arsenic to Zinc. New York: Viking, 2011. Print.

"Einsteinium." Periodic Table. Royal Soc. of Chemistry, 2015. Web. 21 Sept. 2015.

Ghiorso, Albert. "Einsteinium and Fermium." Chemical & Engineering News. Amer. Chemical Soc., 2003. Web. 22 Sept. 2015.

Gray, Theodore. The Elements: A Visual Exploration of Every Known Atom in the Universe. New York: Black Dog, 2009. Print.

Haire, Richard G. "Einsteinium." The Chemistry of the Actinide and Transactinide Elements. Ed. Lester R. Morss, Norman M. Edelstein, and Jean Fuger. 4th ed. Vol. 3. Dordrecht: Springer, 2010. 1577–620. Print.

Morss, Lester. "Einsteinium (Es)." Encyclopædia Britannica. Encyclopædia Britannica, 12 June 2013. Web. 21 Sept. 2015.

Parsons, Paul, and Gail Dixon. The Periodic Table: A Visual Guide to the Elements. New York: Quercus, 2014. Print.

"Technical Data for Einsteinium." The Photographic Periodic Table of the Elements. Element Collection, n.d. Web. 21 Sept. 2015.