Californium vs Einsteinium

Side-by-side comparison of Californium (Cf, element 98) and Einsteinium (Es, element 99) by atomic structure and physical properties.

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PropertyCf Californium Es Einsteinium
Atomic number9899
SymbolCfEs
NameCaliforniumEinsteinium
Categoryactinideactinide
Standard Atomic Weight251 u252 u
Period77
GroupN/AN/A
Blockff
Phase at STPSolidSolid
Electron configuration[Rn]5f107s2[Rn]5f117s2
Oxidation states[2, 3, 4, 5][2, 3, 4]
Electronegativity (Pauling)1.31.3
Electron affinity-1.01 eV-0.3 eV
Density1.51e+4 kg/m³8840 kg/m³
Melting point899.85 °C859.85 °C
Boiling pointN/AN/A
Discovery year19501952

Key Differences

PropertyCf CaliforniumEs Einsteinium
Standard Atomic Weight251 u ↓ lower252 u ↑ higher
Density1.51e+4 kg/m³ ↑ higher8840 kg/m³ ↓ lower
Melting point899.85 °C ↑ higher859.85 °C ↓ lower
Electron affinity-1.01 eV ↓ lower-0.3 eV ↑ higher
Electron configuration[Rn]5f107s2 [Rn]5f117s2
Discovery year1950 1952