Plutonium vs Americium

Side-by-side comparison of Plutonium (Pu, element 94) and Americium (Am, element 95) by atomic structure and physical properties.

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PropertyPu Plutonium Am Americium
Atomic number9495
SymbolPuAm
NamePlutoniumAmericium
Categoryactinideactinide
Standard Atomic Weight244 u243 u
Period77
GroupN/AN/A
Blockff
Phase at STPSolidSolid
Electron configuration[Rn]5f67s2[Rn]5f77s2
Oxidation states[2, 3, 4, 5, 6, 7, 8][2, 3, 4, 5, 6, 7]
Electronegativity (Pauling)1.281.3
Electron affinity-0.5 eV0.1 eV
Density1.984e+4 kg/m³1.2e+4 kg/m³
Melting point639.85 °C1175.85 °C
Boiling point3227.85 °C2010.85 °C
Discovery year19411944

Key Differences

PropertyPu PlutoniumAm Americium
Standard Atomic Weight244 u ↑ higher243 u ↓ lower
Density1.984e+4 kg/m³ ↑ higher1.2e+4 kg/m³ ↓ lower
Melting point639.85 °C ↓ lower1175.85 °C ↑ higher
Boiling point3227.85 °C ↑ higher2010.85 °C ↓ lower
Electronegativity (Pauling)1.28 ↓ lower1.3 ↑ higher
Electron affinity-0.5 eV ↓ lower0.1 eV ↑ higher
Electron configuration[Rn]5f67s2 [Rn]5f77s2
Discovery year1941 1944