Element 100
Fermium (Fm)
Fermium (Fm) is element 100 of the periodic table, a actinide in period 7 (f-block) with an atomic mass of 257 and is a solid at standard conditions.
At a glance
- Atomic number
- 100
- Symbol
- Fm
- Atomic mass
- 257 u
- Category
- Actinides
- Period
- 7
- Block
- f-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 5f12 7s2
- Shorthand configuration
- [Rn] 5f12 7s2
- Electrons per shell
- 2, 8, 18, 32, 30, 8, 2
- Oxidation states
- +2, +3
Physical properties
- Melting point
- 1800 K
- Density
- 9.7 g/cm3
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 1.3
- First ionization energy
- 629 kJ/mol
- Electron affinity
- 34 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| Fm-257 | 257.09511 | — | Half-life 100.5 days |
Common uses
- Scientific research only
Discovery
- Year
- 1952
- Discovered by
- Albert Ghiorso
- Country
- USA