100Actinide · Group 3 · Period 7
Fermium
Fermium (Fm) is element 100, a actinide in the f-block — group 3, period 7. It is a solid at room temperature with 7 electron shells (2, 8, 18, 32, 30, 8, 2) and an atomic mass of 257 u.
- Atomic mass
- 257.0 u
- Phase · STP
- solid
- Melting
- 1800 K · 1527 °C
- Boiling
- —
- Electronegativity
- 1.3
- Density
- —
Photograph — U.S. Department of Energy, Public domain, via Wikimedia Commons
Identity
- Atomic number
- 100
- Standard atomic weight
- 257.0 u
- Category
- Actinide
- Group
- 3
- Period
- 7
- Block
- f-block
- Oxidation states
- +3
Physical properties
- Melting point
- 1800 K · 1527 °C
- Boiling point
- —
- Density
- —
- Molar heat capacity
- —
- Atomic radius
- —
- Electron affinity
- 33.96 kJ/mol
Atomic structure
100protons
157neutrons
100electrons
2valence e⁻
- Noble-gas notation
- [Rn] 5f12 7s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f12
- Electrons per shell
- 2, 8, 18, 32, 30, 8, 2
Periodic trends
Where Fermium ranks across all 118 elements.
Discovery
- Discovered
- 1952
- Discovered by
- Lawrence Berkeley National Laboratory
- Named by
- —
- Appearance
- —