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100Fm257

Fermium

ActinidesBlock fPeriod 7solid at 20 °C
Configuration :
[Rn] 5f¹² 7s²
Atomic mass :
257 u
3D Bohr-model representation of the Fermium atom (symbol Fm, atomic number Z=100). Electron shell configuration: 2, 8, 18, 32, 30, 8, 2 electrons.
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Bohr model · educational

Electron configuration

Full1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f¹² 7s²
Short[Rn] 5f¹² 7s²
Valence electrons14
KLMNOPQ shells
K2
L8
M18
N32
O30
P8
Q2

Electronegativity

Pauling1.3
Allen
Mulliken (eV)

Atomic radii

Empirical
Calculated
Covalent
Van der Waals

Successive ionisation energies

I₁627 kJ/mol
Electron affinity

Oxidation states

+2+3
Bold states = most common.
Period 7Block fFamily Actinides
Sources : NIST Atomic Weights & Isotopic Compositions, IUPAC Recommendations, CODATA. Methodology