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About Americium

Americium Bohr

Americium, a transuranic radioelement with a silvery white appearance and a density similar to lead, was discovered in 1944 at Argonne National Laboratory at the University of Chicago, by a team of scientists led by Glenn T. Seaborg. It was later synthesized at University of California, Berkeley. The process of isolating americium from curium was so arduous that the researchers had taken to calling the elusive element pandemonium. Americium occupies the spot below Europium on the very last row of the periodic table, and was given its name as a result as of this association with another element named after a continent.

Americium is the only synthetic element that has found a common consumer use--as the ionization source in commercial and residential smoke detectors. Additionally, americium is used as neutron source in neutron probes and neutron radiography, and as a portable source of gamma rays and alpha particles in medical, scientific, and industrial uses. Americium is also a starting material for the production of other synthetic elements. Though americium is produced fairly routinely in nuclear reactors, the complexity of the separation procedures necessary to isolate it from other elements ensures that the supply of the pure element remains low, and the material remains quite expensive.

Americium Properties

Americium Bohr ModleAmericium is a Block F, Group 3, Period 7 element. The number of electrons in each of Americium's shells is 2, 8, 18, 32, 25, 8, 2 and its electron configuration is [Rn] 5f7 7s2. The americium atom has a radius of 173.pm and its Van der Waals radius is 244.pm. In its elemental form, CAS 7440-35-9, americium has a silvery white appearance. Americium was discovered by Glenn T. Seaborg, Ralph A. James, Stanley G. Thompson and Albert Ghiorso in 1944. It was the fourth synthetic transuranic element to be discovered and was named after the continent of North America.

Americium is artificially produced in small quantities for research purposes and use in smoke detectors. Due to its radioactivity, americium is harmful. Americium information, including properties, research, applications and other useful facts are discussed below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity and thermal properties are included.

Symbol: Am
Atomic Number: 95
Atomic Weight: 243
Element Category: Actinide
Group, Period, Block: n/a, 7, f
Color: silvery white
Other Names: Americio
Melting Point: 1176 °C, 2148.8 °F, 1449.15 K
Boiling Point: 2011 °C, 3651.8 °F, 2284.15 K
Density: 13670 kg·m3
Liquid Density @ Melting Point: N/A
Density @ 20°C: 13.67 g/cm3
Density of Solid: 13780 kg·m3
Specific Heat: N/A
Superconductivity Temperature: 0.6 [or -272.5 °C (-458.5 °F)] K
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 14.4
Heat of Vaporization (kJ·mol-1): 238.5
Heat of Atomization (kJ·mol-1): 266
Thermal Conductivity: 10 W·m-1·K-1
Thermal Expansion: N/A
Electrical Resistivity: 0.69 µΩ·m
Tensile Strength: N/A
Molar Heat Capacity: 62.7 J·mol-1·K-1
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: N/A
Pauling Electronegativity: 1.3
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.2
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.7
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 95
Protons: 95
Neutrons: 148
Electron Configuration: [Rn] 5f7 7s2
Atomic Radius: 173 pm
Atomic Radius,
non-bonded (Å):
2.44
Covalent Radius: 180±6 pm
Covalent Radius (Å): 1.73
Van der Waals Radius: 244 pm
Oxidation States: 6, 5, 4, 3, 0
Phase: Solid 
Crystal Structure: hexagonal
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) Unknown
1st Ionization Energy: 578 kJ·mol-1
2nd Ionization Energy: N/A
3rd Ionization Energy: N/A
CAS Number: 7440-35-9
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [Am]
InChI Identifier: InChI=1S/Am
InChI Key: LXQXZNRPTYVCNG-UHFFFAOYSA-N
PubChem CID: 23966
ChemSpider ID: 22405
Earth - Total: N/A
Mercury - Total: N/A
Venus - Total: N/A
Earth - Seawater (Oceans), ppb by weight: N/A
Earth - Seawater (Oceans), ppb by atoms: N/A
Earth -  Crust (Crustal Rocks), ppb by weight: N/A
Earth -  Crust (Crustal Rocks), ppb by atoms: N/A
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso
Discovery Date: 1944
First Isolation: N/A

Americium Isotopes

Americium is an artificial element. It has no stable isotopes.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
231Am 231.04556(32)# 30# s β+ to 231Pu; α to 227Np N/A N/A 1747.71301 -
232Am 232.04659(32)# 79(2) s β+ to 232Pu; α to 228Np N/A N/A 1754.824951 -
233Am 233.04635(11)# 3.2(8) min β+ to 233Pu; α to 229Np; SF N/A N/A 1763.0059813 -
234Am 234.04781(22)# 2.32(8) min β+ to 234Pu; α to 230Np; SF N/A N/A 1769.845947 -
235Am 235.04795(13)# 9.9(5) min β+ to 235Pu; α to 231Np 5/2-# N/A 1777.697998 -
236Am 236.04958(11)# 3.6(1) min β+ to 236Pu; α to 232Np N/A N/A 1784.334961 -
237Am 237.05000(6)# 73.0(10) min EC to 237Pu; α to 233Np 5/2(-) N/A 1792.032471 -
238Am 238.05198(5) 98(2) min EC to 238Pu; α to 234Np 1+ N/A 1798.234253 -
239Am 239.0530245(26) 11.9(1) h EC to 239Pu; α to 235Np (5/2)- N/A 1805.336182 -
240Am 240.055300(15) 50.8(3) h EC to 240Pu; α to 236Np (3-) N/A 1811.293579 -
241Am 241.0568291(20) 432.2(7) a α to 237Np; SF 5/2- 1.61 1817.935059 -
242Am 242.0595492(20) 16.02(2) h EC to 242Pu; β- to 242Cm 1- 0.388 1823.472534 -
243Am 243.0613811(25) 7,370(40) a α to 239Np; SF 5/2- 1.61 1829.8396 -
244Am 244.0642848(22) 10.1(1) h β- to 244Cm (6-)# N/A 1835.203247 -
245Am 245.066452(4) 2.05(1) h β- to 245Cm (5/2)+ N/A 1841.25708 -
246Am 246.069775(20) 39(3) min β- to 246Cm (7-) N/A 1846.23291 -
247Am 247.07209(11)# 23.0(13) min β- to 247Cm (5/2)# N/A 1852.145996 -
248Am 248.07575(22)# 3# min β- to 248Cm N/A N/A 1856.807983 -
249Am 249.07848(32)# 1# min β- to 249Cm N/A N/A 1862.332031 -
Americium Elemental Symbol

Recent Research & Development for Americium

  • O.S. Valu, D. Staicu, O. Beneš, R.J.M. Konings, P. Lajarge, Heat capacity, thermal conductivity and thermal diffusivity of uranium–americium mixed oxides, Journal of Alloys and Compounds, Volume 614, 25 November 2014
  • Denis Horlait, Richard Caraballo, Florent Lebreton, Christophe Jégou, Pascal Roussel, Thibaud Delahaye, Self-irradiation and oxidation effects on americium sesquioxide and Raman spectroscopy studies of americium oxides, Journal of Solid State Chemistry, Volume 217, September 2014
  • Yury Malyshkin, Igor Pshenichnov, Igor Mishustin, Walter Greiner, Monte Carlo modeling of spallation targets containing uranium and americium, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 334, 1 September 2014
  • Marcus Christl, Xiongxin Dai, Johannes Lachner, Sheila Kramer-Tremblay, Hans-Arno Synal, Low energy AMS of americium and curium, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 331, 15 July 2014
  • E. Remy, S. Picart, T. Delahaye, I. Jobelin, F. Lebreton, D. Horlait, I. Bisel, P. Blanchart, A. Ayral, Fabrication of uranium-americium mixed oxide pellet from microsphere precursors: application of CRMP process, Journal of Nuclear Materials, Available online 5 July 2014
  • Huang Huang, Songdong Ding, Ning Liu, Yuxuan Wu, Dongping Su, Song Huang, Extraction of trivalent americium and europium from nitric acid solution with a calixarene-based diglycolamide, Separation and Purification Technology, Volume 123, 26 February 2014
  • Denis Horlait, Florent Lebreton, Aurélie Gauthé, Marie Caisso, Bénédicte Arab-Chapelet, Sébastien Picart, Thibaud Delahaye, Americium-based oxides: Dense pellet fabrication from co-converted oxalates, Journal of Nuclear Materials, Volume 444, Issues 1–3, January 2014
  • Chikashi Suzuki, Tsuyoshi Nishi, Masami Nakada, Tomohito Tsuru, Mitsuo Akabori, Masaru Hirata, Yoshiyuki Kaji, DFT study on the electronic structure and chemical state of Americium in an (Am,U) mixed oxide, Journal of Physics and Chemistry of Solids, Volume 74, Issue 12, December 2013
  • B. Raditzky, S. Sachs, K. Schmeide, A. Barkleit, G. Geipel, G. Bernhard, Spectroscopic study of americium(III) complexes with nitrogen containing organic model ligands, Polyhedron, Volume 65, 28 November 2013
  • Yong Lu, Yu Yang, Fawei Zheng, Bao-Tian Wang, Ping Zhang, Electronic, mechanical, and thermodynamic properties of americium dioxide, Journal of Nuclear Materials, Volume 441, Issues 1–3, October 2013
  • J. Lamontagne, Y. Pontillon, E. Esbelin, S. Béjaoui, B. Pasquet, P. Bourdot, J.M. Bonnerot, Determining the americium transmutation rate and fission rate by post-irradiation examination within the scope of the ECRIX-H experiment, Journal of Nuclear Materials, Volume 440, Issues 1–3, September 2013
  • Florent Lebreton, Denis Horlait, Thibaud Delahaye, Philippe Blanchart, Fabrication and characterization of U1-xAmxO2±d compounds with high americium contents (x = 0.3, 0.4 and 0.5), Journal of Nuclear Materials, Volume 439, Issues 1–3, August 2013
  • I. Sato, M. Suto, S. Miwa, T. Hirosawa, S. Koyama, Americium and plutonium release behavior from irradiated mixed oxide fuel during heating, Journal of Nuclear Materials, Volume 437, Issues 1–3, June 2013
  • Claude Degueldre, Cedric Cozzo, Matthias Martin, Daniel Grolimund, Cyprian Mieszczynski, Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide, Journal of Solid State Chemistry, Volume 202, June 2013
  • Kosuke Tanaka, Masahiko Osaka, Shuhei Miwa, Takashi Hirosawa, Ken Kurosaki, Hiroaki Muta, Masayoshi Uno, Shinsuke Yamanaka, Preparation and characterization of the simulated burnup americium-containing uranium–plutonium mixed oxide fuel, Journal of Nuclear Materials, Volume 420, Issues 1–3, January 2012
  • Florent Lebreton, Damien Prieur, Aurélien Jankowiak, Magaly Tribet, Caroline Leorier, Thibaud Delahaye, Louis Donnet, Philippe Dehaudt, Fabrication and characterization of americium, neptunium and curium bearing MOX fuels obtained by powder metallurgy process, Journal of Nuclear Materials, Volume 420, Issues 1–3, January 2012
  • Alok Rout, Sanat Karmakar, K.A. Venkatesan, T.G. Srinivasan, P.R. Vasudeva Rao, Room temperature ionic liquid diluent for the mutual separation of europium(III) from americium(III), Separation and Purification Technology, Volume 81, Issue 2, 22 September 2011
  • K. Maeda, K. Katsuyama, Y. Ikusawa, S. Maeda, Short-term irradiation behavior of low-density americium-doped uranium–plutonium mixed oxide fuels irradiated in a fast reactor, Journal of Nuclear Materials, Volume 416, Issues 1–2, 1 September 2011
  • J. Lamontagne, S. Béjaoui, K. Hanifi, Ch. Valot, L. Loubet, Swelling under irradiation of MgO pellets containing americium oxide: The ECRIX-H irradiation experiment, Journal of Nuclear Materials, Volume 413, Issue 3, 30 June 2011
  • P. Gotcu-Freis, J.-Y. Colle, J.-P. Hiernaut, R.J.M. Konings, The vaporisation behaviour of americium dioxide by use of mass spectrometry, Journal of Nuclear Materials, Volume 409, Issue 3, 28 February 2011