#99 EinsteiniumEinsteinium is a synthetic element with symbol Es and atomic number 99. A member of the actinide series, it is the seventh transuranic element. Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein. Atomic mass:(252.0) amu Melting point: Unknown Boiling point: Unknown Density:293 K: Unknown |