99Es

Einsteinium

Actinide

Einsteinium (Es) is element 99, an actinide, in period 7 of the periodic table. Its atomic mass is usually given as 252, it melts at 860 °C and boils at 996 °C. Discovered by Lawrence Berkeley Lab, 1952.

Atomic Number99

SymbolEs

NameEinsteinium

Atomic Weight252 u

CategoryActinide

Period7

Melting Point860 °C

Boiling Point996 °C

Density8.84 g/cm³

Electron Config[Rn] 5f11 7s2

Discovered ByLawrence Berkeley Lab, 1952

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