100 predicted 2 · 8 · 18 · 32 · 30 · 8 · 2

Fermium, Fm, element 100

Actinide· Period 7· f-block

Configuration [Rn]5f127s2

Atomic weight
257Da
Phase
solid, predicted
Density
9.7g/cm³, predicted
Melting point
1,800.15K, predicted 1,527 °C
Boiling point
No data
Electronegativity
1.3

Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes, most stable is Fm-257 with a half-life of 10 days. First identified by Albert Ghiorso and associates in the debris of the first hydrogen-bomb explosion in 1952. Description from mendeleev.

Back to the table
The outermost shell: the valence electronsThe inner shellsThe nucleus One bead for each electron, on the ring of its shell, counted from the nucleus out. The rings turn at their own pace; the model is Bohr's picture of the atom, which places electrons in shells but not on true orbits.

Atomic properties

4 of 5 fields have a value for fermium

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.
257Da
Source: mendeleev
Electron configuration
[Rn]5f127s2
Source: mendeleev
Electron configuration in full The electron configuration with the noble-gas core written out.
1s22s22p63s23p63d104s24p64d104f145s25p65d105f126s26p67s2
Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.
2 · 8 · 18 · 32 · 30 · 8 · 2
Source: Worked outfrom electron configuration

No data uncertainty of the atomic weight.