Fermium (Fm)

Actinides · Period 7 · Unknown / not established

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Element identity

Atomic number (Z): 100
Symbol: Fm
Atomic weight / isotope mass number: [257]
Category: Actinides
Physical state (reference): Unknown / not established
Period: 7
Group (reference): 3
Block: f

Physical properties

Appearance: Not available
Density: Not available
Melting point: 1800 K / 1527 °C / 2781 °F
Boiling point: Not available
Sublimation point: Not available

Atomic and material properties

Electron configuration: [Rn] 5f¹² 7s²
Electrons per shell: K2 L8 M18 N32 O30 P8 Q2
Oxidation states: 2, 3
Electronegativity (Pauling): 1.3
Atomic radius: Not available
Covalent radius: Not available
Molar ionization energies: 1st: 627 kJ·mol⁻¹ 2nd: 1225 kJ·mol⁻¹ 3rd: 2363 kJ·mol⁻¹ 4th: 3792 kJ·mol⁻¹
Thermal conductivity: Not available
Molar heat capacity: Not available
Crystal structure: Not available
CAS number: 7440-72-4

Property source: Wikipedia — Fermium, adapted from the Nuclides App snapshot. Quoted conditions and qualifiers are retained.

Sources and interpretation

Snapshot exported 24 October 2026 from the element assets used by Nuclides. Properties are a reference compilation, not a new evaluation. Missing values are shown as “Not available”. Density and phase depend on temperature, pressure and allotrope; retained conditions are part of the quoted property.

Atomic weight is dimensionless. Parentheses give uncertainty in the last quoted digits. A single integer in square brackets is an isotope mass number, not a standard atomic weight. The snapshot can differ from current evaluations; consult CIAAW standard atomic weights and the IUPAC periodic table for current values and conventions.

Element properties in the App snapshot are adapted from Wikipedia. Each element page links to its source article; text adaptations are available under CC BY-SA 4.0. No third-party images are included.

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