Skip to main content

Americium

95
Am
243

About Americium

Americium Bohr

Americium, a transuranic radioelement with a silvery white appearance and a density similar to lead, was discovered in 1944 at the Argonne National Laboratory by a team of scientists led by Glenn T. Seaborg. It was later synthesized at the 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 the other 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 applications. 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.

General Properties

Symbol:Am
Atomic Number:95
Atomic Weight:243
Element Category:Actinide
Group, Period, Block:n/a, 7, f
Color:silvery white
Other Names:Americio

Physical Properties

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

Chemical Properties

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

Identifiers

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

Abundance

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

History

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.

 

NuclideIsotopic MassHalf-LifeMode of DecayNuclear SpinMagnetic MomentBinding Energy (MeV)Natural Abundance
(% by atom)
231Am231.04556(32)#30# sß+ to 231Pu; a to 227NpN/AN/A1747.71301-
232Am232.04659(32)#79(2) sß+ to 232Pu; a to 228NpN/AN/A1754.824951-
233Am233.04635(11)#3.2(8) minß+ to 233Pu; a to 229Np; SFN/AN/A1763.0059813-
234Am234.04781(22)#2.32(8) minß+ to 234Pu; a to 230Np; SFN/AN/A1769.845947-
235Am235.04795(13)#9.9(5) minß+ to 235Pu; a to 231Np5/2-#N/A1777.697998-
236Am236.04958(11)#3.6(1) minß+ to 236Pu; a to 232NpN/AN/A1784.334961-
237Am237.05000(6)#73.0(10) minEC to 237Pu; a to 233Np5/2(-)N/A1792.032471-
238Am238.05198(5)98(2) minEC to 238Pu; a to 234Np1+N/A1798.234253-
239Am239.0530245(26)11.9(1) hEC to 239Pu; a to 235Np(5/2)-N/A1805.336182-
240Am240.055300(15)50.8(3) hEC to 240Pu; a to 236Np(3-)N/A1811.293579-
241Am241.0568291(20)432.2(7) aa to 237Np; SF5/2-1.611817.935059-
242Am242.0595492(20)16.02(2) hEC to 242Pu; ß- to 242Cm1-0.3881823.472534-
243Am243.0613811(25)7,370(40) aa to 239Np; SF5/2-1.611829.8396-
244Am244.0642848(22)10.1(1) hß- to 244Cm(6-)#N/A1835.203247-
245Am245.066452(4)2.05(1) hß- to 245Cm(5/2)+N/A1841.25708-
246Am246.069775(20)39(3) minß- to 246Cm(7-)N/A1846.23291-
247Am247.07209(11)#23.0(13) minß- to 247Cm(5/2)#N/A1852.145996-
248Am248.07575(22)#3# minß- to 248CmN/AN/A1856.807983-
249Am249.07848(32)#1# minß- to 249CmN/AN/A1862.332031-