99 Es
Actinide
Einsteinium
From nuclear test fallout.
Properties of Einsteinium
- Atomic number (Z)
- 99
- Symbol
- Es
- Atomic mass
- 252 g/mol
- Category
- Actinide
- Group
- 3
- Period
- 7
- Electron configuration
- [Rn] 5f¹¹ 7s²
- Electronegativity (Pauling)
- 1.3
- Atomic radius
- —
- First ionization energy
- 619 kJ/mol
- Melting point
- 1133 K (859.9 °C)
- Boiling point
- 1269 K (995.9 °C)
- Density
- 8.84 g/cm³
- Phase at 25 °C
- Solid
- Discovered
- Discovered in 1952