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252 2

1s22s22p63s23p63d104s24p6 4d105s25p64f145d106s26p65f11 7s2
[ ? ] Transuranic element:
Soft, silvery metal
Radioactive and toxic.

Einsteinium is a chemical element, having the chemical symbol Es. Its atomic number (the number of protons) is 99. It has a standard atomic weight of 252 g•mol −1 and it is a solid in its elemental form.

Einsteinium is considered a member of the "Transuranic" class of elements. At a pressure of 101.325 kPa, it has a melting point of 860 °C. There is no data available regarding its boiling point.

Formally it was named for Albert Einstein, although it was initially called "pandamonium".[1]. Einsteinium was first identified in December 1952 by Albert Ghiorso and co-workers at the University of California, Berkeley in collaboration with the Argonne and Los Alamos National Laboratories. It was found in the fallout from the Ivy Mike nuclear test on November 1, 1952 at Enewetak Atoll in the Pacific Ocean. That test produced the 253 Einsteinium isotope with a half-life of 20 days.[2][3]


  1. Chemistry in Action, Issue 51 From the website of the University of Limerick in Ireland. In the left-hand navigation column, scroll down to Scetion 15, click on it and then read about the letter by Eric Evans on page 8 of the Economist of April 19, 1997
  2. Al Ghiorso's Long and Happy Life From the website of the Lawrence Berkeley National Laboratory (LBNL)
  3. Los Alamos National Laboratory (LANL)