views updated May 21 2018


melting point: 1,133K
boiling point: 1,269K
density: 8.8 +/ g/cc
most common ions: Es3+, Es2+

Einsteinium, the tenth member of the actinide series, was discovered in 1952. Einsteinium and fermium (element 100) were most unexpectedly produced in the explosion of the first U.S. thermonuclear device, "Mike," tested at Eniwetok Atoll in the Pacific Ocean on November 1, 1952. Early analyses of debris from that explosion indicated that something unusual had occurred; the new, very neutron-rich isotope of plutonium, 244Pu, was found during mass spectrometric analyses performed at the Argonne National Laboratory and another isotope of plutonium, 246Pu, was detected at the Los Alamos Scientific Laboratory in the course of analyses of the Pu fractions. Scientists at the Radiation Laboratory at the University of California, Berkeley, using their previous experience with the separation of individual actinide elements, then joined in the search for trans-californium elements (elements of higher atomic number than californium). Tons of coral from the atoll were laboriously processed, and 25399 (half-life 20 days) and 255100 (half-life 20 hours) were positively identified based on the order of their elution (removal) from a cation-exchange resin column with an α -hydroxyisobutyrate solution. Because of the huge, nearly instantaneous neutron flux generated in the explosion, at least seventeen neutrons were successively captured by the 238U in the thermonuclear device, producing uranium isotopes through 255U, many of which β -decayed to higher atomic number elements, thus producing 253Es and 255Fm. After their declassification, these results were published jointly by the Berkeley Radiation Laboratory, the Argonne National Laboratory, and the Los Alamos Scientific Laboratory (Ghiorso et al., p. 1048[L], 1955).

The name einsteinium was chosen for element 99, in honor of the great scientist Albert Einstein. Einsteinium isotopes of masses 241 through 256 are known. All are radioactive, decaying by α -particle emission, electron capture, spontaneous fission , and β -decay. The mass 241 isotope has the shortest half-life (8 seconds), and the mass 252 isotope has the longest (1.29 years). The ground state electronic configuration of the gaseous einsteinium atom is [Rn]5f117s2, analogous to that of its lanthanide homologue (holmium). The most stable ion in aqueous solution is Es3+, but Es2+ and Es4+ have been reported, and the metal is divalent.

see also Actinium; Berkelium; Einstein, Albert; Fermium; Lawrencium; Mendelevium; Neptunium; Nobelium; Plutonium; Protactinium; Radioactivity; Rutherfordium; Thorium; Transmutation; Uranium.

Darleane C. Hoffman


Ghiorso, Albert; Thompson, S. G.; Higgins, G. H.; et al. (1955). "New Elements Einsteinium and Fermium, Atomic Numbers 99 and 100." Physical Review 99:1048[L].

Hoffman, Darleane C.; Ghiorso, Albert; and Seaborg, Glenn T. (2000). The Transuranium People: The Inside Story. Singapore: World Scientific Publishing.

Seaborg, Glenn T., and Loveland, Walter D. (1990). The Elements beyond Uranium. New York: Wiley.

Einsteinium (revised)

views updated May 29 2018


Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.


Einsteinium is a member of the actinide family. The actinide elements are found in Row 7 of the periodic table, a chart that shows how chemical elements are related to each other. The actinides fall between radium (element number 88) and rutherfordium (element number 104). They are usually listed in a separate row at the very bottom of the periodic table.

Einsteinium is also a transuranium element. Transuranium elements are those beyond uranium on the periodic table. Uranium has an atomic number of 92, so elements with larger atomic numbers are transuranium elements.




Transuranium element


Discovery and naming

Einsteinium was discovered by a research team from the University of California at Berkeley. The team was led by Albert Ghiorso (1915- ). The element was discovered in the "ashes" after the first hydrogen bomb test in November 1952 at Eniwetok Atoll, Marshall Islands, in the Pacific Ocean. The discovery was a remarkable accomplishment because no more than a hundred millionth of a gram of the element was present. It was detected because of the characteristic radiation it produced.

Element number 99 was named after German-American physicist Albert Einstein (1879-1955). Some people regard Einstein as the greatest scientist who ever lived.

Physical and chemical properties

Too little einsteinium has been prepared to allow scientists to determine its physical and chemical properties.

Occurrence in nature

Einsteinium does not occur naturally in the Earth's crust.


All isotopes of einsteinium are radioactive. The most stable is einsteinium-252. Its half life is 20.47 days. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. A radioactive isotope is one that breaks apart and gives off some form of radiation.

The half life of a radioactive element is the time it takes for half of a sample of the element to break down. For example, suppose that scientists made 10 grams of einsteinium. About three weeks later (20.47 days later), only 5 grams of the element would be left. After another three weeks (20.47 days more), only half of that amount (2.5 grams) would remain.


Einsteinium is not extracted from the Earth's crust.


Einsteinium is sometimes used for research purposes, but it has no practical applications.


There are no commercially important compounds of einsteinium.

Einsteinium was named after the great German-American physicist, Albert Einstein.

Health effects

Scientists know too little about einsteinium to be aware of its health effects. As a radioactive element, however, it does pose a threat to human health.


views updated May 14 2018

einsteinium (symbol Es) Radioactive, synthetic metallic element of the actinide series. The isotope, Es253, was first identified in 1952 by US nuclear scientist Albert Ghiorso (1915– ) and colleagues at the University of California at Berkeley; this was after it was found as a decay product of U238 produced by the first large hydrogen bomb explosion. Eleven isotopes have been identified. Properties: at.no. 99; most stable isotope Es254 (half-life 276 days). See also transuranic elements