Einsteinium
[Rn] 5f¹¹ 7s² · 2 · 8 · 18 · 32 · 29 · 8 · 2
An element first found not in a laboratory but in the radioactive dust of a thermonuclear explosion. Einsteinium turned up in the filters of aircraft flown through the Ivy Mike cloud in 1952.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 99
- Atomic mass
- 252 а.е.м. ≈
- Electron configuration
- [Rn] 5f¹¹ 7s²
- Electrons per shell
- 2 · 8 · 18 · 32 · 29 · 8 · 2
- Block
- f-block
- Group
- no data
- Period
- 7
- Electronegativity (Pauling)
- 1.3
- Electronegativity (Allen)
- 1.3
- Atomic radius
- 245 pm
- Covalent radius
- 165 pm
- Van der Waals radius
- 245 pm
- Ionisation energy 1
- 619 kJ/mol
- Electron affinity
- -28.6 kJ/mol
- Common oxidation states
- +3
- Oxidation states
- +2, +3, +4
Physical properties
- State at 25 °C
- solid
- Density
- 8.84 g/cm³
- Melting point
- 1 133 K · 859.9 °C
- Boiling point
- 1 269 K · 995.9 °C ≈
- Speed of sound
- no data
Thermal properties
- Heat of fusion
- no data
- Heat of vaporisation
- no data
- Specific heat capacity
- no data
- Thermal conductivity
- no data
Mechanical properties
- Young's modulus
- no data
- Shear modulus
- no data
- Bulk modulus
- no data
- Poisson ratio
- no data
- Mohs hardness
- no data
- Brinell hardness
- no data
Electrical and magnetic properties
- Electrical resistivity
- no data
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- face-centred cubic (fcc)
- Lattice constants
- a = 575 pm
Abundance
- In the crust
- 0 mg/kg
- In the ocean
- 0 mg/L
- In the universe
- 0 mg/kg
- In the human body
- 0 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 252Es | — | 1.29 yr | α |
| 254Es | — | 275.69 d | α |
Einsteinium-252, half-life 472 days, is the longest-lived. Practical work uses einsteinium-253 and einsteinium-254.
Discovery
- Year of discovery
- 1952
- Discovered by
- Albert Ghiorso and colleagues
- Where
- USA
- Origin of the name
- after Albert Einstein
History
The discovery was classified for nearly three years because it revealed details of the bomb's design. It was announced in 1955 and named after Albert Einstein — who was still alive, and did not know.
Where it occurs
Absent from nature.
How it is produced
In high-flux reactors by prolonged irradiation. World output is on the order of a milligram a year.
Role in living things
No biological role.
Safety
Extremely radiotoxic. Its own radiation destroys the crystal lattice of a sample within weeks.
Uses
- A target for synthesising heavier elements, mendelevium among them
- Fundamental research into heavy actinide chemistry
Curiosities
- Einsteinium was found in the fallout of a thermonuclear test, not made in an accelerator.
- In 2021 a bond length in an einsteinium complex was measured for the first time, on a 200-nanogram sample.
- Einsteinium's radiation is intense enough that a sample destroys itself from within.
- Einstein died in 1955, the same year the element bearing his name was announced.