About

Einsteinium is a synthetic element named in honor of Albert Einstein. It was discovered unexpectedly in the debris of the first hydrogen bomb explosion in 1952. It is highly radioactive and has only ever been produced in tiny, sub-microgram amounts. Its extreme radioactivity and difficulty of production mean it is used solely for fundamental scientific research, primarily for creating heavier elements.

Atomic Properties

Atomic Number99

Atomic Weight252 u

Neutrons (common)153

Electron Configuration[Rn] 5f¹¹ 7s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 5f¹¹ 7s²

Electrons per Shell2, 8, 18, 32, 29, 8, 2

Electronegativity1.3

Electron Affinity-28.6 kJ/mol

Oxidation States+2, +3

Ionic Radius92.8 pm

Periodic Table Position

Group3

Period7

BlockF

Chemical SeriesActinoids

Physical Properties

State at STPsolid

Appearancesilvery, metallic

Crystal Structurefcc

Magnetic Orderingparamagnetic

Thermal Properties

Melting Point1,133 K

Boiling Point1,269 K

Thermal Conductivity10 W/(m·K)

Heat of Fusion9.41 kJ/mol

Discovery

Discovered byAlbert Ghiorso, Stanley G. Thompson, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey

Discovery Year1,952

Occurrencesynthetic

CAS Number7429-92-7

Electron Configuration

Energy

↿⇂

1s

↿⇂

2s

↿⇂

2p

↿⇂

3s

↿⇂

3p

↿⇂

4s

↿⇂

3d

↿⇂

4p

↿⇂

5s

↿⇂

4d

↿⇂

5p

↿⇂

6s

↿⇂

4f

↿⇂

5d

↿⇂

6p

↿⇂

7s

↿⇂

↿

5f

6d

7p

Isotopes of Einsteinium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
²⁵²Es	252.082980	—	471.7 d	Alpha Decay, Electron Capture