Einsteinium

Einsteinium was discovered unexpectedly in the debris of the first hydrogen bomb test (Ivy Mike, 1952), uranium-238 had captured up to 17 neutrons during the explosion to form new heavy elements. Named after Albert Einstein, it was the seventh transuranic element found and required top-secret analysis of coral samples from the test site.

• Atomic Number9999 protons, 99 electrons
• Atomic Mass252.0830 u99× heavier than hydrogen
• State at Room TempSolidSolid
• DensityNot measured
• Melting / Boiling859.9°C
• Discovered1952

What is Einsteinium?

Einsteinium has 99 protons. Its most stable isotope, Es-252, has a half-life of 471.7 days. Only microgram quantities are produced per year. Its chemistry has been studied using nanogram amounts. Discovered in 1952 by Albert Ghiorso and colleagues, officially announced in 1955 after declassification.

Fact Einsteinium is element 99, symbol Es. As an actinide, it is part of the f-block of the periodic table: one of 15 radioactive elements from actinium (89) to lawrencium (103). All actinides are radioactive; none has a stable isotope. They are produced in nuclear reactors and by decay of heavier elements, and their chemistry has been studied using only microgram or nanogram quantities.

Where you find Einsteinium

On Earth

Einsteinium does not occur in significant natural abundance. It is produced only artificially, by bombarding heavier actinide targets with neutrons or lighter ions in nuclear reactors or particle accelerators. World production is measured in nanograms or picograms, a few billion atoms at most per year.

How we use Einsteinium

At element 99, practical applications are limited by the extreme difficulty of production and the intense radioactivity. Einsteinium has 99 protons Future applications in targeted cancer radiotherapy are being investigated using alpha-emitting actinide isotopes bound to tumour-targeting molecules.

How it was discovered

Einsteinium has 99 protons. Its most stable isotope, Es-252, has a half-life of 471.7 days. Only microgram quantities are produced per year. Its chemistry has been studied using nanogram amounts. Discovered in 1952 by Albert Ghiorso and colleagues, officially announced in 1955 after declassification.

Deeper dive: einsteinium and the actinide series

The actinides (elements 89-103) form the lower of the two rows below the main body of the periodic table. They represent the filling of the 5f electron subshell. Unlike the lanthanides (the upper row), the actinides show greater variety in their chemistry because the 5f, 6d and 7s orbitals are close in energy. The early actinides, thorium through neptunium, can show many different oxidation states (e.g. uranium from +3 to +6). The heavier actinides increasingly resemble the lanthanides in preferring the +3 state.

All actinides beyond bismuth (83) are radioactive. The lightest, thorium, protactinium and uranium, have long enough half-lives to survive from the formation of the solar system. Neptunium and beyond are almost entirely synthetic, produced in nuclear reactors or accelerators. The transuranic elements were created at remarkable facilities including Oak Ridge National Laboratory, the Berkeley Cyclotron, the GSI in Darmstadt and JINR in Dubna.

Moving to 100 protons brings us to the next element on the periodic table.