Einsteinium (Es)
Einsteinium (symbol Es) is the chemical element with atomic number 99: an actinide, solid at 0 °C, radioactive, made artificially, with an atomic mass of 252 u. Discovered in 1952 (Albert Ghiorso et al.).
Einsteinium was discovered in the fallout of the first thermonuclear explosion in history, in 1952. Its discovery was kept secret for three years. At best, only a few milligrams are produced at a time, and it is used solely for research. Its most stable isotope, einsteinium-252, has a half-life of about 470 days.
Key facts
- Atomic number
- 99
- Symbol
- Es
- French name
- Einsteinium
- Atomic mass
- 252 u
- Molar mass
- [252] g/mol
- Family
- Actinides
- Position
- period 7, f-block
- State at 0 °C
- Solid
- Melting point
- 859.9 °C
- Boiling point
- 995.9 °C
- Density
- 8.84 g/cm³
- Electronegativity (Pauling)
- 1.3
- First ionization energy
- 619 kJ/mol
- Atomic radius
- 186 pm
- Electron configuration
- [Rn] 5f¹¹ 7s²
- Radioactive
- yes
- Discovery
- 1952, Albert Ghiorso et al.
Origin of the name
In honor of Albert Einstein.
What does einsteinium look like?
A silvery metal that gives off a bluish glow in the dark because of its intense radioactivity. It releases so much energy that it constantly damages its own crystal lattice.
Where is einsteinium found?
Absent from nature. It is produced in vanishingly small amounts in research reactors.
How is einsteinium produced?
It is made in Oak Ridge's HFIR reactor by irradiating curium with neutrons for months, as a by-product of californium production. Each campaign yields a few milligrams at best, often far less.
Top producers
- United States (Oak Ridge)
What is einsteinium used for?
- Basic research only
- Target for making heavier elements (mendelevium was created this way)
- Studying the chemistry of the heavy actinides
In everyday life
- None — only traces of it exist, in a few laboratories
Role in living things
No biological role. Animal studies show that it settles mainly in the bones and liver.
Hazards of einsteinium
Highly radioactive; it requires shielded facilities. The quantities are so small that the risk is confined to specialized laboratories.
Cosmic origin
- Human-made: Does not exist (or barely) in nature: synthesized in a reactor or accelerator.
History of einsteinium
On November 1, 1952, the United States detonated “Ivy Mike,” the first H-bomb, on Enewetak Atoll in the Pacific. Aircraft flew through the cloud to collect dust on filters. Albert Ghiorso and his Berkeley colleagues found a new element in it, formed when the bomb's uranium captured some fifteen neutrons in one go. Military secrecy was not lifted until 1955.
Did you know?
- The very first identification rested on only about 200 atoms.
- Albert Einstein, who died in April 1955, never saw the public announcement of the element that bears his name.
- In 2021, a Berkeley team managed to measure some of einsteinium's chemical properties with a sample of just 200 nanograms.
Isotopes of einsteinium
No stable isotopes; einsteinium was discovered in the fallout of the first H-bomb, in 1952. No more than a few milligrams of it have ever been made.
- einsteinium-252: radioactive, half-life 1.29 years. The longest-lived.
- einsteinium-253: radioactive, half-life 20.5 days. The first isotope identified, in 1952, in the debris of the “Ivy Mike” test.
- einsteinium-254: radioactive, half-life 276 days. A target for making heavier elements.
Related elements
Same family (actinides): Actinium (Ac), Thorium (Th), Protactinium (Pa), Uranium (U), Neptunium (Np), Plutonium (Pu), Americium (Am), Curium (Cm), Berkelium (Bk), Californium (Cf), Fermium (Fm), Mendelevium (Md), Nobelium (No), Lawrencium (Lr).