Einsteinium

Actinide · atomic number 99

99252EsEinsteiniumSolidActinide

Einsteinium is a synthetic element with symbol Es and atomic number 99. It is the seventh transuranic element, and an actinide. Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein.

Properties of Einsteinium

Element category	Actinide
Atomic number	99
Atomic mass	252 u
Phase at STP	Solid
Group	3
Period	7
Block	f
Electron configuration	[Rn] 5f11 7s2
Electrons per shell	2, 8, 18, 32, 29, 8, 2
Electronegativity (Pauling)	1.3
Melting point	1133 K (860 °C)
Boiling point	1269 K (996 °C)
Density	8.84 g/cm3
Discovered by	Lawrence Berkeley National Laboratory

← Californium · Periodic table · Fermium → Fm

About the actinide group

Mostly radioactive, heavy metals — several made only in reactors — whose fission powers nuclear energy and weapons.

Data: Periodic-Table-JSON (CC BY-SA 3.0) · stored statically on our server. https://en.wikipedia.org/wiki/Einsteinium

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15 elements: Mostly radioactive, heavy metals — several made only in reactors — whose fission powers nuclear energy and weapons.

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8 elements: Superheavy synthetic elements made atom-by-atom, existing for fractions of a second; their true chemistry is still unmeasured.