Einsteinium
Symbol |
Name |
Atomic Number |
Atomic Weight |
Group Number |
Es |
Einsteinium |
99 |
(254) |
|
Standard Sate: solid at 298 K
Color: unknown, but very probably metallic and silvery white or grey in appearance
Einsteinium is radioactive rare earth metal named after Albert Einstein. It is of no commercial importance and only a few of its compounds are known.
(Es), synthetic chemical element of the actinide series in Group IIIb
of the periodic table, atomic number 99. Not occurring in nature,
einsteinium (as the isotope einsteinium-253), produced by intense
neutron irradiation of uranium-238, was identified in December 1952
by Albert Ghiorso and co-workers at Berkeley, Calif., in debris taken
from the first thermonuclear or hydrogen-bomb explosion, in the South
Pacific (November 1952).
The material was first collected on filter paper by drone airplanes
flying through the radioactive-explosion clouds; later, einsteinium
and element 100 (fermium) were positively identified in coral gathered
from Enewetak Atoll. Einsteinium metal has not yet been prepared.
All einsteinium isotopes are radioactive. Mixtures of the isotopes
einsteinium-253 (20.5-day half-life), einsteinium-254 (276-day
half-life), and einsteinium-255 (38.3-day half-life) can be produced
by intensive slow-neutron irradiation of elements of lower atomic
number, such as plutonium. Tracer studies indicate that the +3
oxidation state exists in aqueous solution, presumably as the Es3+ ion;
there is also some evidence for a +2 state. Einsteinium has chemical
properties very similar to those of the other actinide elements in the
tripositive state. Einsteinium-255 and einsteinium-256 eject
electrons (beta particles) to form isotopes of fermium (atomic number
100), and einsteinium-253 was used to produce mendelevium
(atomic number 101). atomic number 99 stablest isotope 254 valence
2,3 electronic config. 2-8-18-32-29-8-2 or(Rn)5f 117s2
"einsteinium" Encyclop�dia Britannica Online.
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