Curium(III) oxide

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Curium(III) oxide
La2O3structure.jpg
Names
IUPAC name
Curium(III) oxide
Systematic IUPAC name
Curium(3+) oxide
Other names
Curic oxide

Curium sesquioxide

Curium trioxide
Identifiers
3D model (JSmol)
PubChem CID
  • InChI=1S/2Cm.3O/q2*+3;3*-2 X mark.svgN
    Key: TYZFTGHDCPRRBH-UHFFFAOYSA-N X mark.svgN
  • [O--].[O--].[O--].[Cm+3].[Cm+3]
Properties
Cm2O3
Molar mass 542 g·mol−1
Melting point 2,265 °C (4,109 °F; 2,538 K)
Structure
Hexagonal, hP5, Body-Centered Cubic, Monoclinic
P-3m1, No. 164
Related compounds
Other cations
Gadolinium(III) oxide, Curium hydroxide, Curium trifluoride, Curium Tetrafluoride, Curium Trichloride, Curium Triiodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Curium(III) oxide is a compound composed of curium and oxygen with the chemical formula Cm2O3. It is a crystalline solid with a unit cell that contains two curium atoms and three oxygen atoms. The simplest synthesis equation involves the reaction of curium(III) metal with O2−: 2 Cm3+ + 3 O2− ---> Cm2O3. [1] Curium trioxide can exist as five polymorphic forms. [2] [3] Two of the forms exist at extremely high temperatures, making it difficult for experimental studies to be done on the formation of their structures. The three other possible forms which curium sesquioxide can take are the body-centered cubic form, the monoclinic form, and the hexagonal form. [3] [4] Curium(III) oxide is either white or light tan in color and, while insoluble in water, is soluble in inorganic and mineral acids. [5] [6] Its synthesis was first recognized in 1955. [7]

Contents

Synthesis

Curium sesquioxide can be prepared in a variety of ways.

Route 1: The traditional aerosolization reaction utilizes curium metal as the starting material. While curium metal has been discovered to naturally exist as a mixture of 87.4% 244Cm, 8.4% 243Cm, 3.9% other curium isotopes, and ~0.3% of the daughter nuclide, plutonium, in most aerosolized syntheses of curium(III) oxide, curium metal is purified through solvent extraction of curium nitrate and bis(2-ethylhexyl) phosphoric acid in toluene to remove the plutonium. [6] NH3OH is then added to the purified curium nitrate, and the resulting precipitate is collected and rinsed with deionized water. The precipitate (Cm2O3) is resuspended in solvent and aerosolized with some sort of high output aerosol generator (ex: Lovelace nebulizer). [6]

Route 2: In other aerosolizations, instead of the addition of NH3OH to the purified curium nitrate, ammonium hydroxide is utilized to adjust the pH value of the solution to 9. The increased basicity of the solution creates a curium hydroxide precipitate. This precipitate is then collected through filtration and resuspended in deionized water, and a nebulizer is then used to aerosolize the product. [9]

239Pu + n ---> 240Pu + n ---> 241Pu + n ---> 242Pu + n ---> 243Pu+ β− ---> 243Am + n ---> 244Am + β− ---> 244Cu. [10]

However, 244curium is one of the more unstable curium isotopes, so any structural data obtained for compounds containing 244Cm may deviate from the expected as a result of structural damage. [3] It has been experimentally determined that, within one day, 244CmO2's lattice parameter increases by a factor of 0.2%. [3] This has been hypothesized to be a result of the weakening interatomic interactions between curium(IV) and the neighboring oxide groups as a result of alpha-decay. This affects the thermal conductivity of curium oxides, causing it to exponentially decrease over time as the effects of alpha-decay strengthen. [11] Abnormal phase transitions have also been reported and have been theorized to be a result of induced self-irradiation, either by 244Cm or the presence of leftover 244Am from incomplete radioactive decay. [3] [11]

Structure

The body-centered cubic and monoclinic forms are the most common polymorphic forms of curium trioxide, produced by the chemical reactions detailed above. Their crystalline structures are very similar. One of the polymorphs of curium trioxide - the body-centered cubic form - spontaneously transforms to the hexagonal form after several weeks. [8] This transformation is undergone upon spontaneous 244Cm alpha decay, which produces radiation damage effects within the cubic crystal lattice to distort it to that of hexagonal. [3] Although not experimentally proven, there is speculation that monoclinic curium trioxide may be an intermediate form in between the transformation of the cubic form to that of the hexagonal. The body-centered cubic form of curium trioxide exists below temperatures of 800 °C, the monoclinic form between 800 °C and 1615 °C, and the hexagonal form above 1615 °C. [8]

Crystallography

The lattice parameters for three of the polymorphic structures of curium sesquioxide are given below.

Hexagonal:

Hexagonal.svg

Data Table [8] [12] Temperature (°C)Lengths of a (Å)Uncertainty (Å)Lengths of c (Å)Uncertainty (Å)
16153.8450.0056.0920.005
--*3.4960.00311.3310.005

(*: No specific temperature has been stated to produce the lengths listed in the second row. [8] [12] )

Monoclinic:

Monoclinic cell.svg

Data Table [13] Temperature (°C)Lengths of a (Å)Lengths of b (Å)Lengths of c (Å)
2114.257**8.92**3.65**

(**: None of these lengths contained given uncertainties. [13] )

Cubic:

Lattice body centered cubic.svg

Data Table [8] Temperature (°C)Lengths of a (Å)Uncertainty (Å)
2110.970.01

Data

Ever since the discovery (and isolation) of 248Cm, the most stable curium isotope, experimental work on the thermodynamic properties of curium sesquioxide (and other curium compounds) has become more prevalent. However, 248Cm can only be obtained in mg samples, so data collection for 248Cm-containing compounds takes longer than that for compounds which predominantly contain other curium isotopes. [3] The data table below reflects a large variety of data collected specifically for curium sesquioxide, some of which is purely theoretical, but most of which have been obtained from 248Cm-compounds. [3] [4] [7] [14] [15] [16]

Ground State F-Configuration for MetalApproximate Melting Point (°C)Magnetic Susceptibility (μb)Uncertainty (μb)Enthalpy of Formation (kJ/mol)Uncertainty (kJ/mol)Average Standard Molar Entropy (J/molK)Uncertainty (J/molK)
f7 (Cm3+)2265*7.89**0.04**-400**5**157***5***

(*: Different syntheses of curium trioxide have been shown to produce compounds with different experimental melting points. The melting point given in this data table is merely an average of those collected from the references. [15] [16] )

(**: Characteristic of the monoclinic form.)

(***: Various experiments have calculated different estimates of the standard molar entropy for curium trioxide: Moskin has reported a standard molar entropy of 144.3 J/molK (no given uncertainty). Westrum and Grønvold have reported a value of 160.7 J/molK (no given uncertainty), and Konings’ value is reported to be 167 +/- 5 J/molK. [14] )

Toxicology

Curium metal is a radionuclide and emits alpha particles upon radioactive decay. [14] Although it has a half life of 34 ms, many curium oxides, including curium sesquioxide, have half lives nearing thousands of years. [7] Curium, in the form of curium sesquioxide, can be inhaled into the body, causing many biological defects. The LD50 of curium is 3 micro-Ci through ingestion and inhalation and 1 micro-Ci through absorption through the skin. [17] In one experiment, rats were introduced to aerosolized particulates of curium(III) oxide. Although the experiment proved that inhaled 244Cm2O3 is half as carcinogenic as compared to inhaled 239PuO2, the rats still suffered from many biological deformities, such as skin lesions, malignant tumors, and lung neoplasms. [9] A small amount of the rat population was able to clear particulate curium sesquioxide from the lungs, suggesting that curium sesquioxide is partially soluble in lung fluid. [9]

Applications

Curium(III) oxide is heavily used in industrial grade-reactions and reagents. [15] As recently as 2009, actinide oxides, such as curium sesquioxide, are being considered for storage uses (in the form of heavily durable ceramic glassware) for the transportation of the light-and-air sensitive fission and transmutation target substances. [15]

Other reactions

Curium sesquioxide will spontaneously react with gaseous oxygen at high temperatures. [12] At lower temperatures, a spontaneous reaction will occur over a period of time. Curium trioxide reacted with water has been hypothesized to afford a hydration reaction, but little experimentation has been done to prove the hypothesis. [12] Curium sesquioxide has been shown to not react with nitrogen gas, spontaneously or non-spontaneously. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Americium</span> Chemical element, symbol Am and atomic number 95

Americium is a synthetic chemical element; it has symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element europium and was thus named after the Americas by analogy.

The actinide or actinoid series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. The actinide series derives its name from the first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide.

<span class="mw-page-title-main">Berkelium</span> Chemical element, symbol Bk and atomic number 97

Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

<span class="mw-page-title-main">Curium</span> Chemical element, symbol Cm and atomic number 96

Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium with alpha particles. This was then sent to the Metallurgical Laboratory at University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium.

<span class="mw-page-title-main">Antimony trioxide</span> Chemical compound

Antimony(III) oxide is the inorganic compound with the formula Sb2O3. It is the most important commercial compound of antimony. It is found in nature as the minerals valentinite and senarmontite. Like most polymeric oxides, Sb2O3 dissolves in aqueous solutions with hydrolysis. A mixed arsenic-antimony oxide occurs in nature as the very rare mineral stibioclaudetite.

A sesquioxide is an oxide of an element, where the ratio between the number of atoms of that element and the number of atoms of oxygen is 2:3. For example, aluminium oxide Al2O3 and phosphorus(III) oxide P4O6 are sesquioxides. Many sesquioxides contain a metal in the +3 oxidation state and the oxide ion O2−, e.g., aluminium oxide Al2O3, lanthanum(III) oxide La2O3 and iron(III) oxide Fe2O3. Sesquioxides of iron and aluminium are found in soil. The alkali metal sesquioxides are exceptions because they contain both peroxide O2−2 and superoxide O−2 ions, e.g., rubidium sesquioxide Rb4O6 is formulated (Rb+)4(O2−2)(O−2)2. Sesquioxides of metalloids and nonmetals are better formulated as covalent, e.g. boron trioxide B2O3, dinitrogen trioxide N2O3 and phosphorus(III) oxide P4O6; chlorine trioxide Cl2O3 and bromine trioxide Br2O3 do not have oxidation state +3 on the halogen.

<span class="mw-page-title-main">Gadolinium(III) oxide</span> Chemical compound

Gadolinium(III) oxide (archaically gadolinia) is an inorganic compound with the formula Gd2O3. It is one of the most commonly available forms of the rare-earth element gadolinium, derivatives of which are potential contrast agents for magnetic resonance imaging.

<span class="mw-page-title-main">Californium compounds</span>

Few compounds of californium have been made and studied. The only californium ion that is stable in aqueous solutions is the californium(III) cation. The other two oxidation states are IV (strong oxidizing agents) and II (strong reducing agents). The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate or hydroxide. If problems of availability of the element could be overcome, then CfBr2 and CfI2 would likely be stable.

<span class="mw-page-title-main">Berkelium compounds</span> Any chemical compound having at least one berkelium atom

Berkelium forms a number of chemical compounds, where it normally exists in an oxidation state of +3 or +4, and behaves similarly to its lanthanide analogue, terbium. Like all actinides, berkelium easily dissolves in various aqueous inorganic acids, liberating gaseous hydrogen and converting into the trivalent oxidation state. This trivalent state is the most stable, especially in aqueous solutions, but tetravalent berkelium compounds are also known. The existence of divalent berkelium salts is uncertain and has only been reported in mixed lanthanum chloride-strontium chloride melts. Aqueous solutions of Bk3+ ions are green in most acids. The color of the Bk4+ ions is yellow in hydrochloric acid and orange-yellow in sulfuric acid. Berkelium does not react rapidly with oxygen at room temperature, possibly due to the formation of a protective oxide surface layer; however, it reacts with molten metals, hydrogen, halogens, chalcogens and pnictogens to form various binary compounds. Berkelium can also form several organometallic compounds.

<span class="mw-page-title-main">Einsteinium(III) oxide</span> Chemical compound

Einsteinium(III) oxide is an oxide of the synthetic actinide einsteinium which has the molecular formula Es2O3. It is a colourless solid.

<span class="mw-page-title-main">Actinide chemistry</span> Branch of nuclear chemistry

Actinide chemistry is one of the main branches of nuclear chemistry that investigates the processes and molecular systems of the actinides. The actinides derive their name from the group 3 element actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide. All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell; lawrencium, a d-block element, is also generally considered an actinide. In comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence. The actinide series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.

<span class="mw-page-title-main">Thorium compounds</span> Any chemical compound having at least one atom of thorium

Many compounds of thorium are known: this is because thorium and uranium are the most stable and accessible actinides and are the only actinides that can be studied safely and legally in bulk in a normal laboratory. As such, they have the best-known chemistry of the actinides, along with that of plutonium, as the self-heating and radiation from them is not enough to cause radiolysis of chemical bonds as it is for the other actinides. While the later actinides from americium onwards are predominantly trivalent and behave more similarly to the corresponding lanthanides, as one would expect from periodic trends, the early actinides up to plutonium have relativistically destabilised and hence delocalised 5f and 6d electrons that participate in chemistry in a similar way to the early transition metals of group 3 through 8: thus, all their valence electrons can participate in chemical reactions, although this is not common for neptunium and plutonium.

<span class="mw-page-title-main">Americium(III) oxide</span> Chemical compound

Americium(III) oxide or americium sesquioxide is an oxide of the element americium. It has the empirical formula Am2O3. Since all isotopes of americium are only artificially produced, americium (III) oxide has no natural occurrence. The colour depends on the crystal structure, of which there are more than one. It is soluble in acids.

<span class="mw-page-title-main">Berkelium(IV) oxide</span> Chemical compound

Berkelium(IV) oxide, also known as berkelium dioxide, is a chemical compound with the formula BkO2. This compound slowly decays to californium(IV) oxide. It can be converted to berkelium(III) oxide by hydrogen reduction at 600 °C.

Curium compounds are compounds containing the element curium (Cm). Curium usually forms compounds in the +3 oxidation state, although compounds with curium in the +4, +5 and +6 oxidation states are also known.

<span class="mw-page-title-main">Berkelium(III) nitrate</span> Chemical compound

Berkelium(III) nitrate is the berkelium salt of nitric acid with the formula Bk(NO3)3. It commonly forms the tetrahydrate, Bk(NO3)3·4H2O, which is a light green solid. If heated to 450 °C, it decomposes to berkelium(IV) oxide and 22 milligrams of the solution of this compound is reported to cost one million dollars.

Einsteinium compounds are compounds that contain the element einsteinium (Es). These compounds largely have einsteinium in the +3 oxidation state, or in some cases in the +2 and +4 oxidation states. Although einsteinium is relatively stable, with half-lives ranging from 20 days upwards, these compounds have not been studied in great detail.

Protactinium compounds are compounds containing the element protactinium. These compounds usually have protactinium in the +5 oxidation state, although these compounds can also exist in the +2, +3 and +4 oxidation states.

Americium compounds are compounds containing the element americium (Am). These compounds can form in the +2, +3, and +4, although the +3 oxidation state is the most common. The +5, +6 and +7 oxidation states have also been reported.

<span class="mw-page-title-main">Curium(IV) oxide</span> Chemical compound

Curium(IV) oxide is an inorganic chemical compound of curium and oxygen with the chemical formula CmO2. Since all isotopes of curium are man-made, the compound does not occur in nature.

References

  1. ↑ 8. N.A. (2010). "Study of oxychloride compound formation in chloride melt by spectroscopic methods." Radiochemical Division/Research Institute of Atomic Reactors. pp. 1-17.
  2. ↑ Cunningham, B. B. (1964). "Chemistry of the Actinide Elements". Annual Review of Nuclear Science . 14: 323–346. Bibcode:1964ARNPS..14..323C. doi:10.1146/annurev.ns.14.120164.001543.
  3. 1 2 3 4 5 6 7 8 Milman, V., Winkler, B., and C.J. Pickard (2003). “Crystal Structures of Curium Compounds: An Ab Initio Study.” Journal of Nuclear Materials (322): 165-179.
  4. 1 2 Petit, L., Svane, A., Szotek, Z., Temmerman, W.M., and G. M. Stocks (2009). “Electronic structure and ionicity of actinide oxides from first principles calculations.” Materials Science and Technology Division, Oak Ridge National Laboratory. pp. 1-12.
  5. ↑ Norman M. Edelstein; James D. Navratil; Wallace W. Schulz (1984). Americium and curium chemistry and technology. D. Reidel Pub. Co. pp. 167–168.
  6. 1 2 3 4 Helfinstine, Suzanne Y., Guilmette, Raymond A., and Gerald A. Schlapper (1992). “In Vitro Dissolution of Curium Oxide Using a Phagolysosomal Simulant Solvent System.” Environmental Health Perspectives (97): 131-137.
  7. 1 2 3 Morss, L. R., Fuger, J., Goffart, J. and R.G. Haire (1983). “Enthalpy of Formation and Magnetic Susceptibility of Curium Sesquioxide, Cm203.” Inorganic Chemistry (22):1993-1996.
  8. 1 2 3 4 5 6 7 Wallmann, J.C. (1964). “A Structural Transformation of Curium Sesquioxide.” Journal of Inorganic and Nuclear Chemistry (26): 2053-2057.
  9. 1 2 3 4 Lundgren, D. L. , Hahn, F. F., Carlton, W. W., Griffith, W. C., Guilmette, R. A., and N. A. Gillett (1997). “Dose Responses from Inhaled Monodisperse Aerosols of 244Cm203 in the Lung, Liver and Skeleton of F344 Rats and Comparison with 239Pu02.” Radiation Research (5): 598-612.
  10. ↑ Stevens, C. M., Studier, M. H., Fields, P. R. , Meck, J. F., Sellers, P. A., Friedman, A. M., Diamond H., and J. R. Huizenga (1954). “Evidence for Quadrivalent Curium: X-Ray Data on Curium Oxides.” Communications to the Editor (7): 1707-1708.
  11. 1 2 S.E. Lemehov *, V. Sobolev, and P. Van Uffelen (2003). "Modelling thermal conductivity and self-irradiation effects in mixed oxide fuels." Journal of Nuclear Materials (320): 66–76.
  12. 1 2 3 4 5 Lumetta, Gregg J., Thompson, Major C., Penneman, Robert A., and P. Gary Eller (2006). The Chemistry of the Actinide and Transactinide Elements. “Curium: Chapter Nine.” Springer Pub. Co. Vol.3. pp. 1397-1443.
  13. 1 2 Rimshaw, S. J., and E. E. Ketchen (1967). “Curium Data Sheets.” Oak Ridge National Laboratory - Union Carbide Corporation. pp. 42-102.
  14. 1 2 3 Konings, R.J.M (2001). “Estimation of the Standard Entropies of some Am(III) and Cm(III) Compounds.” Journal of Nuclear Materials (295): 57-63.
  15. 1 2 3 4 Smith, Paul Kent (1969). “Melting Point of Curium Trioxide (Cm2O3).” Journal of Inorganic and Nuclear Chemistry (31): 241-245.
  16. 1 2 Smith, Paul Kent (1970). “High-Temperature Evaporation and Thermodynamic Properties of Cm2O3.” The Journal of Chemical Physics (52): 4964-4972.
  17. ↑ “Radionuclide Data Sheet: Curium.” University of California, San Diego. n.d.1.
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