Americium

Americium (Am)

Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes. Am-243 is the most stable isotope, with a half-life of 7.95*10^3 years. Discovered by Glenn T. Seaborg and associates in 1945, it was obtained by bombarding Uranium-238 with alpha particles.
Atomic Number95
Atomic Weight243
Mass Number231
Group
Period7
Blockf
Protons95 p+
Neutrons136 n0
Electrons95 e-
Americium microscope.jpg Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
175 pm
Atomic Volume
Covalent Radius
166 pm
Metallic Radius
Ionic Radius
121 pm
Crystal Radius
135 pm
Van der Waals radius
244 pm
Density
Boiling Point
2,880 K
Melting Point
1,267 K
Electrons per shell2, 8, 18, 32, 25, 8, 2
Electronegativity
Electrophilicity
Proton Affinity
Electron Affinity
Ionization Potential
Heat of Vaporization
238.5 kJ/mol
Heat of Fusion
Heat of Formation
284 kJ/mol
Molar Heat Capacity
Specific Heat Capacity
Thermal Conductivity
Gas Basicity
Dipole Polarizability
131 a₀
C6 Dispersion Coefficient
Oxidation States2, 3, 4, 5, 6
Color
Silver
Crystal StructureSimple Hexagonal ()
Lattice Constant
Bulk Modulus
Electrical Resistivity
Electron Configuration[Rn] 5f7 7s2
Magnetic Ordering
Magnetic Susceptibility
PhaseSolid
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryActinides, Actinides
CAS Group
IUPAC Group
Glawe Number39
Mendeleev Number26
Pettifor Number42
Geochemical Class
Goldschmidt Classsynthetic
Radioactivity
RadioactiveYes ☢️
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
Abundance in Oceans
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universena

Isotopes of Americium

Stable Isotopes
Unstable Isotopes
231Am 232Am 233Am 234Am 235Am 236Am 237Am 238Am 239Am 240Am 241Am 242Am 243Am 244Am 245Am 246Am 247Am 248Am 249Am

History

Americium-241 was first identified in 1944 by Glenn T. Seaborg, Ralph A. James, Leon O. Morgan and Albert Ghiorso at the metallurgical laboratory at the University of Chicago. It was produced by irradiating plutonium with neutrons during the Manhattan Project. Americium was first isolated as a pure compound by Burris Cunningham in 1945, at the University of Chicago. Named after America

DiscoverersG.T.Seaborg, R.A.James, L.O.Morgan, A.Ghiorso
Discovery LocationUnited States
Discovery Year1945
Name OriginNamed for the American continent, by analogy with europium.
Americium is harmful due to its radioactivity
Americium often enters landfills from discarded smoke detectors

Uses

Americium is used in commercial ionization chamber smoke detectors, as well as in neutron sources and industrial gauges. Americium-241 has been used as a portable source of both gamma rays and alpha particles for a number of medical and industrial uses. It is also used as a target material in nuclear research to make even heavier elements. Americium-241 is currently used in smoke detectors.

Sources

Produced by bombarding plutonium with neutrons.