Einsteinium
Actinidesolidblock f
An element discovered in the fallout of the first hydrogen bomb test, found in coral debris before anyone had deliberately set out to make it.
| Atomic number | 99 |
| Mass number (longest-lived isotope) | 252 g/mol |
| This element has no stable isotope, so it has no standard atomic weight. The figure above is the mass number of its longest-lived isotope — a convention, not a measurement of a natural mixture. | |
| Group · period | f-block series · 7 |
| Electron configuration | [Rn] 5f¹¹ 7s² |
About Einsteinium
The Ivy Mike thermonuclear test of November 1952 subjected uranium to a neutron flux so intense that individual nuclei captured fifteen or more neutrons before decaying, and filter papers flown through the mushroom cloud turned out to contain two new elements, 99 and 100. Both discoveries stayed classified until 1955. Einsteinium's longest-lived isotope lasts 471 days and total world inventory is measured in fractions of a milligram, so its chemistry is studied on samples of a few hundred nanograms; a 2021 Berkeley study finally measured a basic bond length using about 200 ng. Einstein, a lifelong pacifist, was reportedly not consulted about having a bomb-derived element named after him, and died before the naming became public.
Moles from Mass (n = m/M)
Opens with M = 252 g/mol already filled in
Gas Density from Molar Mass
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Faraday's Law of Electrolysis (m = QM/nF)
Opens with M = 252 g/mol already filled in
Ion Concentration as CaCO₃ Equivalent
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Acid Feed to Reduce Alkalinity
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