Einsteinium
Atomic Data
| Atomic Number | 99 |
| Symbol | Es |
| Atomic Weight | 252 u |
| Density (STP) | N/A |
| Melting Point | 859.85 °C (1133 K) |
| Boiling Point | N/A °C (None K) |
| Electronegativity | 1.3 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f11 6s2 6p6 7s2 |
| Oxidation States | +2, +3 |
| Phase at STP | Solid |
| Category | Actinoid |
| Period / Group | 7 / None |
| CAS Number | 7429-92-7 |
Electron Configuration
[Rn] 5f11 7s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| N | 4 | 4f | 14 | 60 |
| O | 5 | 5s | 2 | 62 |
| O | 5 | 5p | 6 | 68 |
| O | 5 | 5d | 10 | 78 |
| O | 5 | 5f | 11 | 89 |
| P | 6 | 6s | 2 | 91 |
| P | 6 | 6p | 6 | 97 |
| Q | 7 | 7s | 2 | 99 |
| Total | 99 | 99 | ||
Isotopes of Einsteinium
Einsteinium has two naturally occurring stable isotopes. The most abundant is ²⁵²Es, comprising None% of all naturally occurring Einsteinium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Einsteinium-252 | ²⁵²Es | 99 | 153 | trace | Stable |
| Einsteinium-253 | ²⁵³Es | 99 | 154 | trace | Stable |
Abundance & Occurrence
Einsteinium is present in Earth's crust at approximately trace amounts by mass and at approximately trace amounts by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Alpha and gamma radiation: Einsteinium-254 (t½ = 276 days, alpha emitter) is highly radiotoxic; working quantities are sub-microgram, but even nanogram quantities of Es-254 require handling in specially designated radiological facilities.
- Extreme scarcity: Only microgram quantities of einsteinium have ever been produced; it is handled exclusively in dedicated nuclear research facilities by trained radiochemists in alpha-rated glove boxes.
- Radiation dose at small scale: Despite tiny quantities, the specific activity of einsteinium isotopes is high enough that contamination events could deliver significant localised tissue doses: rigorous contamination monitoring is essential.
- Regulatory controls: Einsteinium production and handling require nuclear regulatory authority licensing; all quantities are subject to strict nuclear material accountancy and safeguards reporting.
Einsteinium in the Real World
Real-World Uses
- Nuclear and radiochemistry research: Einsteinium-253 (t½ = 20.5 d) and Es-254 (t½ = 276 d) are produced in microgram quantities in the HFIR reactor; they are used to study heavy actinide chemistry, measure atomic spectroscopic properties, and as target material for producing still-heavier elements.
- Fundamental chemistry studies: The first synthesis of einsteinium in macroscopic quantities (nanograms) in 2021 enabled the first determination of its ionic radius by X-ray absorption spectroscopy, confirming predictions of how the 5f electron shell contracts across the actinide series.
- No commercial applications: All einsteinium isotopes are intensely radioactive and available only in picogram to nanogram quantities; no practical applications outside fundamental research exist or are anticipated.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is einsteinium used for?
Einsteinium has no practical applications. Quantities have been limited to micrograms produced over weeks or months in high-flux nuclear reactors. Its main use is in fundamental research: studying its chemical and nuclear properties, and as a target for the synthesis of heavier elements such as mendelevium (element 101), which was first made by bombarding einsteinium with helium ions.
How was einsteinium discovered?
Einsteinium was discovered in the debris of the first hydrogen bomb test (Ivy Mike) in November 1952 at Enewetak Atoll. Scientists at Berkeley, Argonne, and Los Alamos analysed coral samples and filter papers from aircraft that had flown through the mushroom cloud. They found that the bomb's uranium-238 had undergone multiple rapid neutron captures to produce heavy transuranic elements including einsteinium-253. The discovery was classified until 1955. It was named in honour of Albert Einstein.
Is einsteinium radioactive?
Yes, all isotopes of einsteinium are radioactive. The longest-lived, Es-252, has a half-life of 471.7 days. The most easily produced for research, Es-253, has a half-life of only 20.5 days. Einsteinium is so intensely radioactive that even microgram quantities generate enough radiation to damage experiments and storage containers over time.
How was einsteinium identified in a nuclear explosion?
In the Ivy Mike thermonuclear test, the enormous flux of neutrons created by the hydrogen bomb rapidly bombarded uranium-238 nuclei, adding up to 17 neutrons in a fraction of a second. These highly neutron-rich uranium nuclei were unstable and rapidly shed electrons (beta decays), converting neutrons to protons and stepping up the atomic number to create elements as heavy as fermium (Z=100). The process mimicked the r-process nucleosynthesis that creates heavy elements in neutron star collisions, but happened in microseconds within the bomb fireball.