Chemical element · Atomic number 99
Einsteinium
Einsteinium in the periodic table: atomic number 99, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Actinide
solid
[252.0830] u
Generated illustrationGenerated illustration, Quanta Study. Not a photograph of a sample.
Generated illustration of Einsteinium; the image does not show a sample of the element.
Transuranic element handled only in specialised laboratories in tiny amounts; no freely licensed sample photograph is available.
Code-native illustration with the Quanta Study mark inside the image; not a photograph, no AI model involved.
Atomic classification
Shell occupancy
Einsteinium in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 18 electrons
- N · n=4
- 32 electrons
- O · n=5
- 29 electrons
- P · n=6
- 8 electrons
- Q · n=7
- 2 electrons
- Electron configuration
- [Rn]7s2 5f11
- Electrons per shell
- 2 · 8 · 18 · 32 · 29 · 8 · 2
- Group
- not reported
- Period
- 7
- Block
- F
- Element category
- Actinide
Physical and chemical properties
- Atomic mass
- [252.0830] u
- Standard state
- solid
- Density
- not reported
- Melting point
- 1,133 K
- Boiling point
- not reported
- Electronegativity
- 1.3 (Pauling)
- First ionisation energy
- 6.42 eV
- Oxidation states
- +3
- Discovery
- 1952
Safety and periodic classification
Safety
Safe handling cannot be inferred from Einsteinium's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Einsteinium is in period 7 and the F block. Its direct neighbours by atomic number are Californium and Fermium. The recorded Pauling electronegativity is 1.3. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.
Where Einsteinium sits among the 118 elements
The table compares the reported values for Einsteinium with every other element that carries the same value in the snapshot. A rank is not a judgement, it is orientation: it says how unusual this value is across the periodic table.
| Value | Einsteinium | Position in the data set |
|---|---|---|
| Melting point | 1,133 K | Rank 54 of 103 elements with a reported value. Highest: Carbon. |
| Electronegativity (Pauling) | 1.3 | Rank 67 of 95 elements with a reported value. Highest: Fluorine. |
| Ionisation energy | 6.42 eV | Rank 62 of 102 elements with a reported value. Highest: Helium. |
All values and ranks come from the PubChem Periodic Table snapshot, retrieved on 2026-07-15. Elements without a reported value are excluded, so the population differs per row.
The neighbours of Einsteinium in the periodic table
- Place in the table
- No group number, period 7, F block. Classified as actinide, solid at standard conditions.
- Direct neighbours
- Atomic number 99. Preceded by Californium, followed by Fermium.
- Discovery
- Recorded in the snapshot as: 1952. Who, where and under what circumstances is not part of that record, so this page carries the sourced year and no discovery narrative.
- Oxidation states
- +3. They follow from the electron configuration [Rn]7s2 5f11 and indicate which compounds to expect.
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