Science Fair Project Encyclopedia
|Name, Symbol, Number||curium, Cm, 96|
|Period, Block||7, f|
|Atomic weight|| amu|
|Atomic radius (calc.)||no data|
|Covalent radius||no data|
|van der Waals radius||no data|
|Electron configuration||[Rn]5f7 6d1 7s2|
|e- 's per energy level||2,8,18,32,25,9,2|
|Oxidation states (Oxide)||3 (amphoteric)|
|State of matter||solid|
|Melting point||1613 K (2444 °F)|
|Boiling point||3383 K (5630 °F)|
|Crystal structure||hexagonal close-packed|
|Magnetic ordering||no data|
|Molar volume||18.05 ×10-6 m3/mol|
|Heat of vaporization||no data|
|Heat of fusion||15 kJ/mol|
|Vapor pressure||no data|
|Velocity of sound||no data|
|Electronegativity||1.3 (Pauling scale)|
|Specific heat capacity||no data|
|Electrical conductivity||no data|
|Thermal conductivity||no data|
|1st ionization potential||581 kJ/mol|
|Most stable isotopes|
|SI units & STP are used except where noted.|
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.
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-242 is useful as a portable energy source due to the fact that it can generate around 2 watts of thermal energy per gram. It is used in pacemakers, remote navigational buoys, and in space missions.
Several curium compounds have been produced. They include: curium dioxide (CmO2), curium trioxide (Cm2O3), curium bromide (CmBr3), curium chloride (CmCl3), curium tetrafluoride (CmF4) and curium iodide (CmI3).
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.
19 radioisotopes of curium have been characterized, with the most stable being Cm-247 with a half-life of 1.56 × 107 years, Cm-248 with a half-life of 3.40 × 105 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 amu (Cm-233) to 252.085 amu (Cm-252).
- 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
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