99
Es
Einsteinium
252
Einsteinium (Es)
ActinidePeriod 7f-block-blockRadioactive
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.
Latin name: Einsteinium
Atomic Number
99
Atomic Mass
252 g/mol
Phase (STP)
Solid
Electron Config.
[Rn] 5f¹¹ 7s²
General
SymbolEs
Atomic Number99
Atomic Mass252 g/mol
CategoryActinide
Period7
Blockf-block
Electron Configuration[Rn] 5f¹¹ 7s²
Valence Electrons13
Coloursilvery (radioactive)
Appearancesilver-colored
Physical Properties
Phase (STP)Solid
Density8.84 g/cm³
Melting Point859.85°C · 1579.73°F · 1133.00 K
Boiling Point995.85°C · 1824.53°F · 1269.00 K
Atomic Properties
Atomic Radius245 pm
Electronegativity1.3 Pauling
Ionization Energy619 kJ/mol
Oxidation States+3, +2
Ion ChargeEs2+/Es3+
Crystal Structure
Crystal Structurehexagonal close-packed
Nuclear & Hazards
RadioactiveYes
Half-life471.7 days (Es-252)
Abundance
In Earth's Crust0.00000000000001%
Discovery & History
Discovery Year1952
Discovered ByAlbert Ghiorso and co-workers
Country of DiscoveryUSA
Isotopes of Einsteinium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Es-252 | — | 471.7 days | α, EC |
| Es-253 | — | 20.47 days | α |
| Es-254 | — | 275.7 days | α |