95
Am
Americium
243
Americium (Am)
ActinidePeriod 7f-block-blockRadioactive
Americium is a radioactive transuranic chemical element with symbol Am and atomic number 95. This member of the actinide series is located in the periodic table under the lanthanide element europium, and thus by analogy was named after the Americas. Americium was first produced in 1944 by the group of Glenn T.Seaborg from Berkeley, California, at the metallurgical laboratory of University of Chicago.
Latin name: Americium
Atomic Number
95
Atomic Mass
243 g/mol
Phase (STP)
Solid
Electron Config.
[Rn] 5f⁷ 7s²
General
SymbolAm
Atomic Number95
Atomic Mass243 g/mol
CategoryActinide
Period7
Blockf-block
Electron Configuration[Rn] 5f⁷ 7s²
Valence Electrons9
Coloursilvery-white metallic
Appearancesilvery white
CAS NumberCAS7440-35-9
Physical Properties
Phase (STP)Solid
Density13.67 g/cm³
Melting Point1175.85°C · 2148.53°F · 1449.00 K
Boiling Point2606.85°C · 4724.33°F · 2880.00 K
Atomic Properties
Atomic Radius244 pm
Electronegativity1.13 Pauling
Ionization Energy578 kJ/mol
Oxidation States+3, +2, +4
Ion ChargeAm2+/Am3+/Am4+
Thermodynamic
Molar Heat62.7 J/(mol·K)
Crystal Structure
Crystal Structuredouble hexagonal close-packed
Nuclear & Hazards
RadioactiveYes
Half-life7.37×10^3 years (Am-243)
Abundance
In Universe0.0000000000001%
In Earth's Crust0.0000000000001%
Discovery & History
Discovery Year1944
Discovered ByGlenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso
Country of DiscoveryUSA
Isotopes of Americium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Am-241 | — | 432.6 years | α |
| Am-242m | — | 141 years | IT |
| Am-243 | — | 7370 years | α |