Erbium vs Thulium

Side-by-side comparison of Erbium (Er, element 68) and Thulium (Tm, element 69) by atomic structure and physical properties.

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PropertyEr Erbium Tm Thulium
Atomic number6869
SymbolErTm
NameErbiumThulium
Categorylanthanidelanthanide
Standard Atomic Weight167.259 u168.93422 u
Period66
GroupN/AN/A
Blockff
Phase at STPSolidSolid
Electron configuration[Xe]4f126s2[Xe]4f136s2
Oxidation states[0, 1, 2, 3][0, 1, 2, 3]
Electronegativity (Pauling)1.241.25
Electron affinity0.312 eV1.029 eV
Density9070 kg/m³9320 kg/m³
Melting point1528.85 °C1544.85 °C
Boiling point2867.85 °C1949.85 °C
Discovery year18431879

Key Differences

PropertyEr ErbiumTm Thulium
Standard Atomic Weight167.259 u ↓ lower168.93422 u ↑ higher
Density9070 kg/m³ ↓ lower9320 kg/m³ ↑ higher
Melting point1528.85 °C ↓ lower1544.85 °C ↑ higher
Boiling point2867.85 °C ↑ higher1949.85 °C ↓ lower
Electronegativity (Pauling)1.24 ↓ lower1.25 ↑ higher
Electron affinity0.312 eV ↓ lower1.029 eV ↑ higher
Electron configuration[Xe]4f126s2 [Xe]4f136s2
Discovery year1843 1879