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Revision as of 23:38, 10 December 2005
Template:Elementbox header Template:Elementbox series Template:Elementbox groupperiodblock Template:Elementbox appearance Template:Elementbox atomicmass gpm Template:Elementbox econfig Template:Elementbox epershell Template:Elementbox section physicalprop Template:Elementbox phase Template:Elementbox density gpcm3nrt Template:Elementbox meltingpoint Template:Elementbox boilingpoint Template:Elementbox heatfusion kjpmol Template:Elementbox vaporpressure katpa Template:Elementbox section atomicprop Template:Elementbox crystalstruct Template:Elementbox oxistates Template:Elementbox electroneg pauling Template:Elementbox ionizationenergies1 Template:Elementbox section miscellaneous Template:Elementbox magnetic Template:Elementbox cas number Template:Elementbox isotopes begin |- ! rowspan="2" style="text-align:right; vertical-align:middle;" | Cm | rowspan="2" style="text-align:center; vertical-align:middle;" | syn | rowspan="2" style="text-align:right; vertical-align:middle;" | 160 days | SF | style="text-align:right;" | - |- | α | style="text-align:right;" | Pu |- ! rowspan="3" style="text-align:right; vertical-align:middle;" | Cm | rowspan="3" style="vertical-align:middle; text-align:center" | syn | rowspan="3" style="vertical-align:middle; text-align:right;" | 29.1 y | α | style="text-align:right;" | Pu |- | ε | style="text-align:right;" | Am |- | SF | style="text-align:right;" | - |- ! rowspan="2" style="text-align:right; vertical-align:middle;" | Cm | rowspan="2" style="text-align:center; vertical-align:middle;" | syn | rowspan="2" style="text-align:right; vertical-align:middle;" | 18.1 y | SF | style="text-align:right;" | - |- | α | style="text-align:right;" | Pu |- ! rowspan="2" style="text-align:right; vertical-align:middle;" | Cm | rowspan="2" style="text-align:center; vertical-align:middle;" | syn | rowspan="2" style="text-align:right; vertical-align:middle;" | 8500 y | SF | style="text-align:right;" | - |- | α | style="text-align:right;" | Pu |- ! rowspan="2" style="text-align:right; vertical-align:middle;" | Cm | rowspan="2" style="text-align:center; vertical-align:middle;" | syn | rowspan="2" style="text-align:right; vertical-align:middle;" | 4730 y | α | style="text-align:right;" | Pu |- | SF | style="text-align:right;" | - |- ! style="text-align:right;" | Cm | style="text-align:center;" | syn | style="text-align:right;" | 15.6 E6 y | α | style="text-align:right;" | Pu |- ! rowspan="2" style="text-align:right; vertical-align:middle;" | Cm | rowspan="2" style="text-align:center; vertical-align:middle;" | syn | rowspan="2" style="text-align:right; vertical-align:middle;" | 340 E3 y | α | style="text-align:right;" | Pu |- | SF | style="text-align:right;" | - |- ! rowspan="3" style="text-align:right; vertical-align:middle;" | Cm | rowspan="3" style="vertical-align:middle; text-align:center" | syn | rowspan="3" style="vertical-align:middle; text-align:right;" | 9000 y | SF | style="text-align:right;" | - |- | α | style="text-align:right;" | Pu |- | β | style="text-align:right;" | Bk Template:Elementbox isotopes end Template:Elementbox footer
Curium is a synthetic element in the periodic table that has the symbol Cm and atomic number 96. A radioactive metallic transuranic element of the actinide series, curium is produced by bombarding plutonium with alpha particles (helium ions) and was named for Marie Curie and her husband Pierre.
Notable characteristics
The isotope curium-248 has been synthesized only in milligram quantities, but curium-242 and curium-244 are made in multigram amounts, which allows for the determination of some of the element's properties. Curium-244 can be made in quantity by subjecting plutonium to neutron bombardment. Very small amounts of curium may exist in uranium ore as a daughter product of natural decay. There are few commercial applications for curium but it may one day be useful in radioisotope thermoelectric generators. Curium bio-accumulates in bone tissue where its radiation destroys bone marrow and thus stops red blood cell creation.
A rare earth homolog, curium is somewhat chemically similar to gadolinium but with a more complex crystal structure. Chemically reactive, its metal is silvery-white in color and the element is more electropositive than aluminium (most trivalent curium compounds are slightly yellow).
Curium has been studied greatly as a potential fuel for Radioisotope thermoelectric generators. Curium-242 can generate up to 120 watts of thermal energy per gram (W/g); Curium-242 very short half-life though makes it undesirable as a power source for long-term use. Curium-242 is the precursor to plutonium-238 which is the most common fuel for RTGs. Curium-244 has also been studied as an energy source for RTGs having a maximum energy density ~3 W/g, but produces a large amount of neutron radiation from spontaneous fission. Curium-243 with a ~30 year half-life and good energy density of ~1.6 W/g would seem to make an ideal fuel, but it produces significant amounts of gamma and beta radiation from radioactive decay products.
They include: curium dioxide (CmO2), curium trioxide (Cm2O3), curium bromide (CmBr3), curium chloride (CmCl3), curium tetrafluoride (CmF4) and curium iodide (CmI3).
History
Curium was first synthesized at the University of California, Berkeley and by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944. The team named the new element after Marie Curie and her husband Pierre who are famous for discovering radium and for their work in radioactivity. It was chemically identified at the Metallurgical Laboratory (now Argonne National Laboratory) at the University of Chicago. It was actually the third transuranium element to be discovered even though it is the second in the series. Curium-242 (half-life 163 days) and one free neutron were made by bombarding alpha particles onto a plutonium-239 target in the 60-inch cyclotron at Berkeley. Louis Werner and Isadore Perlman created a visible sample of curium-242 hydroxide at the University of California in 1947 by bombarding americium-241 with neutrons. Curium was made in its elemental form in 1951 for the first time.
Isotopes
19 radioisotopes of curium have been characterized, with the most stable being Cm-247 with a half-life of 1.56 × 10 years, Cm-248 with a half-life of 3.40 × 10 years, Cm-250 with a half-life of 9000 years, and Cm-245 with a half-life of 8500 years. All of the remaining radioactive isotopes have half-lifes that are less than 30 years, and the majority of these have half lifes that are less than 33 days. This element also has 4 meta states, with the most stable being Cm-244m (t½ 34 ms). The isotopes of curium range in atomic weight from 233.051 u (Cm-233) to 252.085 u (Cm-252).
Nuclear fuel cycle
The MOX which is to be used in power reactors should contain little or no curium as the neutron activation of this element will create californium which is a strong neutron emitter. The californium would pollute the back end of the fuel cycle and increase the dose to workers.
References
- Los Alamos National Laboratory - Curium
- Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
- It's Elemental - Curium
- Human Health Fact Sheet on Curium