Curium

96

americium ← curium → berkelium


Gd
↑
Cm
↓
(Uqh)




periodic table




General


Name, Symbol, Number

curium, Cm, 96


Chemical series
actinides


Group, Period, Block

n/a, 7, f


Appearance
silvery


Atomic mass
(247) g/mol


Electron configuration
[Rn] 5f7 6d1 7s2


Electrons per shell
2, 8, 18, 32, 25, 9, 2


Physical properties


Phase
solid


Density (near r.t.)
13.51 g/cm³


Melting point
1613 K
(1340 °C, 2444 °F)


Boiling point
3383 K
(3110 °C, 5630 °F)


Heat of fusion
? 15 kJ/mol




Vapor pressure


P/Pa
1
10
100
1 k
10 k
100 k


at T/K
1788
1982
 
 
 
 



Atomic properties


Crystal structure
hexagonal close-packed


Oxidation states
3
(amphoteric oxide)


Electronegativity
1.3 (Pauling scale)


Ionization energies

1st: 581 kJ/mol


Miscellaneous


Magnetic ordering
no data


CAS registry number
7440-51-9


Notable isotopes




Main article: Isotopes of curium


iso

NA

half-life

DM

DE (MeV)

DP


242Cm

syn

160 days

SF

-

-


α

6.1

238Pu


243Cm

syn

29.1 y

α

6.169

239Pu


ε

0.009

243Am


SF

-

-


244Cm

syn

18.1 y

SF

-

-


α

5.902

240Pu


245Cm

syn

8500 y

SF

-

-


α

5.623

241Pu


246Cm

syn

4730 y

α

5.475

242Pu


SF

-

-


247Cm

syn

1.56×107 y

α

5.353

243Pu


248Cm

syn

3.40×105 y

α

5.162

244Pu


SF

-

-


250Cm

syn

9000 y

SF

-

-


α

5.169

246Pu


β-

0.037

250Bk


Curium (chemical symbol Cm, atomic number 96) is a radioactive, metallic, transuranic element[1] of the actinide series. It is produced synthetically by bombarding plutonium with alpha particles (helium ions). It was named after Marie Curie and her husband Pierre.

Contents

1 History
2 Notable characteristics

2.1 Isotopes


3 Compounds
4 Applications
5 Nuclear fuel cycle
6 Biological effects
7 See also
8 Notes
9 References
10 External links
11 Credits



Two isotopes of curium (curium-242 and curium-244) can be produced in multigram amounts, making it feasible to study the element's chemical properties. The isotope curium-242 is the precursor to plutonium-238, the most common fuel for radioisotope thermoelectric generators (RTGs) that have been used to power certain space probes. Other curium isotopes (Cu-243, Cu-244) are also being investigated for their potential as fuels for RTGs.

History
Curium was first synthesized at the University of California, Berkeley 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 their work on radioactivity and the discovery of radium and polonium.
Curium was the third transuranic element to be discovered. The isotope curium-242 (half-life 163 days) was made by bombarding a plutonium-239 target with alpha particles in the 60-inch cyclotron at Berkeley. The element was chemically identified at the Metallurgical Laboratory (now Argonne National Laboratory) at the University of Chicago.
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. The elemental form of curium was prepared for the first time in 1951.

Notable characteristics
Curium is an inner transition metal of the actinide series, located in period seven of the periodic table, between americium and berkelium. It does not occur in nature.
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.
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 aluminum (most trivalent curium compounds are slightly yellow).

Isotopes
Many 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 the remaining radioactive isotopes have half-lives of less than 30 years, and the majority of these have half-lives that are less than 33 days. This element also has four 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).

Compounds
Known compounds of curium include the following:

Oxides:
curium dioxide (CmO2)
curium trioxide (Cm2O3)
Halides:
curium tetrafluoride (CmF4)
curium chloride (CmCl3)
curium bromide (CmBr3)
curium iodide (CmI3)
Applications
Curium has been studied extensively as a potential fuel for Radioisotope thermoelectric generators that could be used to power space probes. Curium-242 can generate up to 120 watts of thermal energy per gram (W/g). Its very short half-life, however, makes it unsuitable 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 about three W/g, but produces a large amount of neutron radiation from spontaneous fission. Curium-243, with a roughly 30-year half-life and good energy density (about 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.

Nuclear fuel cycle
If MOX nuclear fuel[2] is to be used in nuclear power reactors, it should contain little or no curium, because neutron activation of this element will create californium, a strong neutron emitter. The californium would pollute the back end of the fuel cycle and increase the dose to workers.

Biological effects
Curium bio-accumulates in bone tissue where its radiation destroys bone marrow and thus stops the production of red blood cells.

See also
Chemical element
Inner transition metal
Metal
Periodic table
Radioactive decay
Notes

↑ "Transuranic elements" are the chemical elements with atomic numbers greater than that of uranium (atomic number 92).

↑ "MOX" (mixed oxide) nuclear fuel is a blend of plutonium with natural uranium, reprocessed uranium, or depleted uranium. Its behavior is similar to that of low enriched uranium (LEU) fuel, and it is an alternative to the LEU used in the light water reactors that predominate nuclear power generation.


ReferencesISBN links support NWE through referral fees
Emsley, John. Nature's Building Blocks: An A–Z Guide to the Elements. Oxford: Oxford Univ. Press, 2001. ISBN 0198503407
Greenwood, N.N., and A. Earnshaw. Chemistry of the Elements 2nd ed. Oxford, UK; Burlington, MA: Butterworth-Heinemann, 1998. ISBN 0750633654
Hampel, Clifford A. The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corp, 1968. ISBN 0442155980
Morss, Lester R., Norman M. Edelstein, and Jean Fuger, eds. The Chemistry of the Actinide and Transactinide Elements. 3rd ed. 5 vols. Joseph J. Katz, adapter. Dordrecht: Springer, 2006. ISBN 1402035551
Stwertka, Albert. Guide to the Elements. Rev. ed. Oxford: Oxford University Press, 1998. ISBN 0195080831
External links
All links retrieved June 23, 2022.

It's Elemental: Curium Jefferson Lab.
Curium. The University of Sheffield and WebElements Ltd.

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