Neptunium vs Plutonium

Side-by-side comparison of Neptunium (Np, element 93) and Plutonium (Pu, element 94) by atomic structure and physical properties.

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PropertyNp Neptunium Pu Plutonium
Atomic number9394
SymbolNpPu
NameNeptuniumPlutonium
Categoryactinideactinide
Standard Atomic Weight237 u244 u
Period77
GroupN/AN/A
Blockff
Phase at STPSolidSolid
Electron configuration[Rn]5f46d17s2[Rn]5f67s2
Oxidation states[2, 3, 4, 5, 6, 7][2, 3, 4, 5, 6, 7, 8]
Electronegativity (Pauling)1.361.28
Electron affinity0.48 eV-0.5 eV
Density2.025e+4 kg/m³1.984e+4 kg/m³
Melting point643.85 °C639.85 °C
Boiling point3901.85 °C3227.85 °C
Discovery year19401941

Key Differences

PropertyNp NeptuniumPu Plutonium
Standard Atomic Weight237 u ↓ lower244 u ↑ higher
Density2.025e+4 kg/m³ ↑ higher1.984e+4 kg/m³ ↓ lower
Melting point643.85 °C ↑ higher639.85 °C ↓ lower
Boiling point3901.85 °C ↑ higher3227.85 °C ↓ lower
Electronegativity (Pauling)1.36 ↑ higher1.28 ↓ lower
Electron affinity0.48 eV ↑ higher-0.5 eV ↓ lower
Electron configuration[Rn]5f46d17s2 [Rn]5f67s2
Discovery year1940 1941