99EsEinsteinium252[Rn] 5f¹¹ 7s²
actinide
Einsteinium
Einsteinium is a synthetic element with symbol Es and atomic number 99. It is the seventh transuranic element, and an actinide. Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
Electrons by shell
Electron configuration
5f11
7s2
86 is the [Rn] core total across six shells.
At a glance
- Atomic number
- 99
- Atomic mass
- 252 u
- Phase
- Solid
- Density
- 8.84 g/cm³
- Melting point
- 1,133 K
- Boiling point
- 1,269 K
- First ionization energy
- 619 kJ/mol
- Electronegativity
- 1.3
- Electron affinity
- -28.6 kJ/mol
- Molar heat capacity
- Unavailable
- Period
- 7
- Appearance
- silver-colored
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.