Einsteinium is the 7th element in the actinide series. The most stable isotope of Einsteinium has 99 protons and electrons and 153 neutrons. There are 19 different (radioactive) isotopes. Einsteinium is named after Albert Einstein. It was found for the first time in 1952 by Albert Ghiorso and his team of scientists in the debris of the first hydrogen bomb explosion, and identified as an element at the University of California, Berkeley.
Einsteinium isotopes have a half-life between 40 and 471 days.
Einsteinium has been used to create the element Mendelevium for the first time in 1955, although no practical uses are known. It has been used before as a calibration marker in a chemical analysis spectrometer.