Promethium vs Samarium

Side-by-side comparison of Promethium (Pm, element 61) and Samarium (Sm, element 62) by atomic structure and physical properties.

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PropertyPm Promethium Sm Samarium
Atomic number6162
SymbolPmSm
NamePromethiumSamarium
Categorylanthanidelanthanide
Standard Atomic Weight145 u150.36 u
Period66
GroupN/AN/A
Blockff
Phase at STPSolidSolid
Electron configuration[Xe]4f56s2[Xe]4f66s2
Oxidation states[2, 3][0, 1, 2, 3]
Electronegativity (Pauling)N/A1.17
Electron affinity0.129 eV0.162 eV
Density7260 kg/m³7520 kg/m³
Melting point1041.85 °C1073.85 °C
Boiling point2999.85 °C1793.85 °C
Discovery year19451879

Key Differences

PropertyPm PromethiumSm Samarium
Standard Atomic Weight145 u ↓ lower150.36 u ↑ higher
Density7260 kg/m³ ↓ lower7520 kg/m³ ↑ higher
Melting point1041.85 °C ↓ lower1073.85 °C ↑ higher
Boiling point2999.85 °C ↑ higher1793.85 °C ↓ lower
Electron affinity0.129 eV ↓ lower0.162 eV ↑ higher
Electron configuration[Xe]4f56s2 [Xe]4f66s2
Discovery year1945 1879