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Einsteinium [Es]
CAS-ID: 7429-92-7
An: 99 N: 153
Am: [252] g/mol
Group Name: Actinoid
Block: f-block  Period: 7 (actinoid)
State: solid at 298 K
Colour: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic
Boiling Point: unknown
Melting Point: 1133K (860°C)
Density: 8.84g/cm3
Discovery Information
Who: Argonne, Los Alamos, U of California
When: 1952
Where: United States
Name Origin
After the scientist Albert Einstein.
 "Einsteinium" in different languages.
Sources
Made by bombarding uranium with neutrons.
Uses
Einsteinium has no known uses.
History
Einsteinium was first identified in December 1952 by Albert Ghiorso at the University of California, Berkeley and another team headed by G.R. Choppin at Los Alamos National Laboratory. Both were examining debris from the first hydrogen bomb test of November 1952 (see Operation Ivy). They discovered the isotope 253Es (half-life 20.5 days) that was made by the nuclear fusion of 15 neutrons with 238U (which then went through seven beta decays). These findings were kept secret until 1955 due to Cold War tensions, however.
In 1961, enough einsteinium was synthesized to prepare a microscopic amount of 253Es. This sample weighed about 0.01 mg and was measured using a special balance. The material produced was used to produce mendelevium. Further einsteinium has been produced at the Oak Ridge National Laboratory's High Flux Isotope Reactor in Tennessee by bombarding 239Pu with neutrons. Around 3 mg was created over a four year program of irradiation and then chemical separation from a starting 1 kg of plutonium isotope.
Notes
In 1961, enough einsteinium was synthesized to prepare a macroscopic amount of 253Es. This sample weighed about 0.01 mg and was measured using a special balance. This material was then used to produce mendelevium.
19 radioisotopes of einsteinium have been characterized, with the most stable being 252Es with a half-life of 471.7 days, 254Es with a half-life of 275.7 days, 255Es with a half-life of 39.8 days, and 253Es with a half-life of 20.47 days. All of the remaining radioactive isotopes have half-lifes that are less than 40 hours, and the majority of these have half lifes that are less than 30 minutes.
Hazards
Einsteinium is a radioactive rare earth metal named after Albert Einstein. It is of no commercial importance and only a few of its compounds are known.