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Photo of light pink systems of americium(III) in focused potassium carbonate (left) and after electrochemical oxidation in ~ a platinum display screen anode to create a golden-brown solution of americium(IV) carbonate facility (right). D. E. Hobart, et al.

You are watching: Continent with a chemical element named for it

(1982) Radiochimica Acta, 31,139.


Atomic Number: 95 Atomic Radius: 244 pm (Van der Waals)
Atomic Symbol: Am Melting Point: 1176 °C
Atomic Weight: 243 Boiling Point: 2607 °C
Electron Configuration: 7s25f7 Oxidation States: 8, 7, 6, 5, 4, 3, 2


Americium was the fourth fabricated transuranic facet to be discovered and also was named after the continent of phibìc America by analogy to its lighter lanthanide homologue, europium, i beg your pardon was called after Europe, the continent of discovery. Americium to be made by glenn Seaborg, Ralph James, Leon Morgan, and also Albert Ghiorso so late in 1944 at the wartime metallurgical laboratory at the university of Chicago. It to be made as the result of successive neutron capture reactions by plutonium isotopes in a atom reactor. The product element was quite challenging to separate based on its suspect properties, which to be incorrect together it turned out. Uneven the lighter previously found transuranium elements placed in the key block of the tasiilaq.net table, americium behaved chemically like the lanthanide collection of elements. That exhibited, for example, the trivalent state together the most stable in aqueous solutions. This behavior and the comparable behavior the the newly discovered element, curium, prompted Glenn Seaborg to boldly and also radically review the tasiilaq.net table and create the actinide collection of elements.

The an initial americium isotope established was the of 241Am, which has actually an alpha decay half-life the 432.2 years to daughter neptunium-237. The initial exploration was share as secret as component of the Manhattan project during people War II, yet the discovery was later on declassified. Seaborg announced the discovery of facets 95, americium 96, and curium ~ above the U.S. Children’s radio show,"The Quiz Kids" five days before his planned presentation at an American Chemical society meeting in November 1945. His notice resulted when one of the young listener asked whether any new transuranium aspect beside plutonium and also neptunium had actually been discovered.


The early stage americium samples weighed a few micrograms; they were barely visible and also were determined by your radioactivity. The an initial substantial quantities of metallic americium to be not all set until 1951 via palliation of americium(III) fluoride v barium metal in high vacuum in ~ 1100 °C, producing up to 200 milligrams. The luster the freshly all set americium steel is white and much more silvery than plutonium or neptunium ready in the exact same manner. It appears to be much more malleable than uranium or neptunium and tarnishes gradually in dried air in ~ room temperature. In solution, oxidation claims III, IV, V, and also VI space known and there is an unsubstantiated case of the visibility of Am(VII). Am(IV) is stormy in acidic media but in strongly simple carbonate services Am(IV) is stable. In fact, in lead carbonate solutions, americium has been shown to it is in the 2nd element after ~ plutonium to have in coexistence all 4 oxidation says simultaneously. Over there are many compounds the americium. That is oxides have actually the most helpful applications.


About 19 isotopes and also 8 atom isomers are known for americium. There are two long-lived alpha-emitters, 241Am and 243Am v half-lives the 432.2 and 7,370 years, respectively, and the nuclear isomer 242Am has a half-life the 141 years. The half-lives of other isotopes and also isomers selection from 0.64 microseconds because that 245Am to 50.8 hours for 240Am. Similar to most various other actinides, the isotope of americium with odd number of neutrons have fairly high price of nuclear fission and also low an essential mass. High purity kilogram quantities are now obtainable for the much longer lived isotopes, 241Am and 243Am.


There are plenty of commercial applications for americium isotopes. Americium-241 has been offered as a portable resource of both gamma rays and alpha particles for a variety of medical and industrial uses. The 60-keV gamma beam emissions native 241Am in such sources have the right to be offered for indirect evaluation of products in radiography and X-ray fluorescence spectroscopy, and for quality regulate in solved nuclear density gauges and nuclear densometers. For example, americium has actually been employed to gauge glass thickness to help create flat glass. Americium-241 is also suitable because that calibration that gamma-ray spectrometers in the low-energy range, due to the fact that its spectrum is composed of nearly a single gamma peak. Americium-241 is additionally used as the ionization resource in commercial smoke detectors. Numerous unusual applications, such together a nuclear battery or fuel for space ships with nuclear propulsion, have been proposed for the isotope 242mAm, yet they room as yet hindered by the scarcity and also high price that this isomer.

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As through all highly radioactive elements, americium and also its compounds need to be handled only in an appropriate laboratory under distinct containment conditions. Although many americium isotopes predominantly emit alpha corpuscle which deserve to be clogged by thin layers of typical materials, countless of the daughter products emit gamma-rays and neutrons which have a lengthy penetration depth. The alpha task from 241Am is around three times the of radium. As soon as gram amounts of 241Am are handled, the extreme gamma task makes exposure a severe problem.

Further Reading

Wolfgang H. Runde and Wallace W. Schulz (2006) "Americium,"" chapter 8 in The Chemistry the the Actinide and also Transactinide Elements, third Edition, L. R. Morss, J. Fuger, and also N. M. Edelstein, Eds, Springer Publishers.

Updated July 2013 by Dr. David Hobart.