Einsteinium

Einsteinium (chemical symbol Es) is a chemical element with atomic number 99. It belongs to the class of elements called transuranic elements whose atomic number are higher than 92, the atomic number of uranium.

Formally it was named for Albert Einstein, although it was initially called Pandamonium. A weapons test: Project Panda, produced the 20-day ^253E isotope in the fallout. Elements 99 and 100 (einsteinium and fermium) were found in debris brought back from the first H-bomb test in the Pacific by Al Ghiorso and co-workers at Berkeley in December 1952