099Actinide · Group 3 · Period 7
Einsteinium
Einsteinium (Es) is element 99, 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, 29, 8, 2) and an atomic mass of 252 u.
- Atomic mass
- 252.0 u
- Phase · STP
- solid
- Melting
- 1133 K · 860 °C
- Boiling
- 1269 K · 996 °C
- Electronegativity
- 1.3
- Density
- 8.84 g/cm³
Photograph — Haire, R. G., US Department of Energy.Touched up by Materialscientist at en.wikipedia., Public domain, via Wikimedia Commons
Identity
- Atomic number
- 99
- Standard atomic weight
- 252.0 u
- Category
- Actinide
- Group
- 3
- Period
- 7
- Block
- f-block
- Oxidation states
- +3
Physical properties
- Melting point
- 1133 K · 860 °C
- Boiling point
- 1269 K · 996 °C
- Density
- 8.84 g/cm³
- Molar heat capacity
- —
- Atomic radius
- 245 pm
- Electron affinity
- -28.6 kJ/mol
Atomic structure
99protons
153neutrons
99electrons
2valence e⁻
- Noble-gas notation
- [Rn] 5f11 7s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f11
- Electrons per shell
- 2, 8, 18, 32, 29, 8, 2
Periodic trends
Where Einsteinium ranks across all 118 elements.
Discovery
- Discovered
- 1952
- Discovered by
- Lawrence Berkeley National Laboratory
- Named by
- —
- Appearance
- silver-colored