Curium
Curium
History
(Pierre and Marie Curie) Although curium follows americium in the periodic system, it was actually known before americium and was the third transuranium element to be discovered. It was identified by Seaborg, James, and Ghiorso in 1944 at the wartime Metallurgical Laboratory in Chicago as a result of helium-ion bombardment of 239Pu in the Berkeley, California, 60-inch cyclotron. Visible amounts (30Mg) of 242Cm, in the form of the hydroxide, were first isolated by Werner and Perlman of the University of California in 1947. In 1950, Crane, Wallmann, and Cunningham found that the magnetic susceptibility of microgram samples of CmF3 was of the same magnitude as that of GdF3. This provided direct experimental evidence for assigning an electronic configuration to Cm+3. In 1951, the same workers prepared curium in its elemental form for the first time. Fourteen isotopes of curium are now known. The most stable, 247Cm, with a half-life of 16 million years, is so short compared to the earth's age that any primordial curium must have disappeared long ago from the natural scene. Minute amounts of curium probably exist in natural deposits of uranium, as a result of a sequence of neutron captures and beta decays sustained by the very low flux of neutrons naturally present in uranium ores. The presence of natural curium, however, has never been detected. 242Cm and 244Cm are available in multigram quantities. 248Cm has been produced only in milligram amounts. Curium is similar in some regards to gadolinium, its rare earth homolog, but it has a more complex crystal structure. Curium is silver in color, is chemically reactive, and is more electropositive than aluminum. Most compounds of trivalent curium are faintly yellow in color. 242 Cm generates about three watts of thermal energy per gram. This compares to one-half watt per gram of 238Pu. This suggests use for curium as a power source. 244Cm is now offered for sale at $100/mg. Curium absorbed into the body accumulates in the bones, and is therefore very toxic as its radiation destroys the red-cell forming mechanism. The maximum permissible total body burden of 244Cm (soluble) in a human being is 0.3 microcurie.
Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.
Last Updated: 12/19/97, CST Information Services Team
http://pearl1.lanl.gov/periodic/elements/96.html [3/6/2001 8:38:24 AM]
Berkelium
Berkelium
History
(Berkeley, home of the University of California) Berkelium, the eighth member of the actinide transition series, was discovered in December 1949 by Thompson, Ghiorso, and Seaborg, and was the fifth transuranium element synthesized. It was produced by cyclotron bombardment of milligram amounts of 241Am with helium ions at Berkeley, California. The first isotope produced had a mass of 243 and decayed with a half-life of 4.5 hours. Ten isotopes are now known and have been synthesized. The evidence of 249Bk with a half-life of 314 days, makes it feasible to isolate berkelium in weighable amounts so that its properties can be investigated with macroscopic quantities. One of the first visible amounts of a pure berkelium compound, berkelium chloride, was produced in 1962. It weighed 1 billionth of a gram. Berkelium probably has not yet been prepared in elemental form, but is expected to be a silvery metal, easily soluble in dilute mineral acids, and readily oxidized by air or oxygen at elevated temperatures to form the oxide. X-ray diffraction methods have been used to identify various compounds. As with other actinide elements, berkelium tends to accumulate in the skeletal system. Because of its rarity, berkelium presently has NO COMMERCIAL OR TECHNOLOGICAL USE.
Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.
Last Updated: 12/19/97, CST Information Services Team
http://pearl1.lanl.gov/periodic/elements/97.html [3/6/2001 8:38:24 AM]
Californium
Californium
For rocket fuel
History
(State and University of California) Californium, the sixth transuranium element to be discovered, was produced by Thompson, Street, Ghioirso, and Seaborg in 1950 by bombarding microgram quantities of 242Cm with 35 MeV helium ions in the Berkeley 60-inch cyclotron. Californium (III) is the only ion stable in aqueous solutions, all attempts to reduce or oxidize californium (III) having failed. The isotope 249Cf results from the beta decay of 249Bk while the heavier isotopes are produced by intense neutron irradiation by the reactions. The existence of the isotopes 249Cf, 250Cf, 251Cf, and 252Cf makes it feasible to isolate californium in weighable amounts so that its properties can be investigated with macroscopic quantities. Californium-252 is a very strong neutron emitter. One microgram releases 170 million neutrons per minute, which presents biological hazards. Proper safeguards should be used in handling californium. Reduction of californium to its metallic state has not yet been accomplished. Because californium is a very efficient source of neutrons, many new uses are expected for it. It has already found use in neutron moisture gauges and in well-logging (the determination of water and oil-bearing layers). It is also being used as a portable neutron source for discovery of metals such as gold or silver by on-the-spot activation analysis. 252-Cf is now being offered for sale by the O.R.N.L. at a cost of $10/mg. As of May, 1975, more than 63 mg have been produced and sold. It has been suggested that californium may be produced in certain stellar explosions, called supernovae, for the radioactive decay of 254Cf (55-day half-life) agrees with the characteristics of the light curves of such explosions observed through telescopes. This suggestion, however, is questioned.
Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.
Last Updated: 12/19/97, CST Information Services Team
http://pearl1.lanl.gov/periodic/elements/98.html [3/6/2001 8:38:24 AM]
Einsteinium
Einsteinium
History
(Albert Einstein) Einsteinium, the seventh transuranic element of the actinide series to be discovered, was identified by Ghiorso and co-workers at Berkeley in December 1952 in debris from the first large thermonuclear explosion, which took place in the Pacific in November, 1952. The 20-day 253Es isotope was produced.
In 1961, enough einsteinium was produced to separate a macroscopic amount of 253Es. This sample weighted about 0.01Mg and was measured using a special magnetic-type balance. 253Es so produced was used to produce mendelevium (Element 101).
About 3Mg of einsteinium has been produced at Oak Ridge National Laboratories by
1.irridiating kilogram quantities of 239Pu in a reactor for several years to produce 242Pu,
2.fabricating the 242Pu into pellets of plutonium oxide and aluminum powder,
3.loading the pellets into target rods for an initial 1-year irradiation at the Savannah River Plant, and
4.irradiating the targets for another 4 months in a HFIR (High Flux Isotopic Reactor).
The targets were then removed for chemical separation of the einsteinium from californium.
Isotopes
Fourteen isotopes of einsteinium are now recognized. 254Es has the longest half-life (275 days).
Properties
Tracer studies using 253Es show that einsteinium has chemical properties typical of a heavy trivalent, actinide element.
Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.
http://pearl1.lanl.gov/periodic/elements/99.html (1 of 2) [3/6/2001 8:38:25 AM]
Einsteinium
Last Updated: 12/19/97, CST Information Services Team
http://pearl1.lanl.gov/periodic/elements/99.html (2 of 2) [3/6/2001 8:38:25 AM]