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| Name = Curium(III) oxide |
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| ImageFile =La2O3structure.jpg |
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|verifiedrevid = 459441755 |
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| ImageName = Curium(III) oxide |
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|Name = Curium(III) oxide |
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|ImageFile = La2O3structure.jpg |
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| IUPACName = Curium(III) oxide |
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|ImageFile_Ref = {{Chemboximage|correct|??}} |
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| OtherNames = Curium sesquioxide |
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|ImageSize = 121 |
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| Section1 = {{Chembox Identifiers |
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|ImageName = Unit cell, ball and stick model of curium(III) oxide |
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| CASNo = 12371-27-6 |
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|IUPACName = Curium(III) oxide |
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| RTECS = |
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|SystematicName = Curium(3+) oxide |
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|OtherNames = Curic oxide<br /> |
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| Section2 = {{Chembox Properties |
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Curium sesquioxide<br /> |
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| Formula = Cm<sub>2</sub>O<sub>3</sub> |
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Curium trioxide |
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| MolarMass = 542.139 g/mol |
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|Section1={{Chembox Identifiers |
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| Appearance = |
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|CASNo = 12371-27-6 |
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| Density = |
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|CASNo_Ref = {{cascite|changed|??}} |
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| Solubility = none |
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|SMILES = .... |
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| MeltingPt = |
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|StdInChI = 1S/2Cm.3O/q2*+3;3*-2 |
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|StdInChI_Ref = {{stdinchicite|changed|chemspider}} |
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|StdInChIKey = TYZFTGHDCPRRBH-UHFFFAOYSA-N |
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|StdInChIKey_Ref = {{stdinchicite|changed|chemspider}} |
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|PubChem = <!-- 18415183 charge error--> |
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| Section3 = {{Chembox Structure |
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|Section2={{Chembox Properties |
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|Cm=2 | O=3 |
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| CrystalStruct = Hexagonal, ] |
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|MeltingPtC = 2265 |
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| SpaceGroup = P-3m1, No. 164 |
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|Section3={{Chembox Structure |
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|CrystalStruct = Hexagonal, ], Body-Centered Cubic, Monoclinic |
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|SpaceGroup = P-3m1, No. 164 |
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|Section4={{Chembox Related |
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|OtherCations = ], ], ], ], ], ]}} |
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'''Curium(III) oxide''' is a ] composed of ] and ] with the chemical formula {{chem2|Cm2O3}}. It is a crystalline solid with a ] that contains two curium atoms and three oxygen atoms. The simplest synthesis equation involves the reaction of curium(III) metal with O<sup>2−</sup>: 2 Cm<sup>3+</sup> + 3 O<sup>2−</sup> ---> Cm<sub>2</sub>O<sub>3</sub>.<ref>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.</ref> Curium trioxide can exist as five ] forms.<ref>{{cite journal|doi=10.1146/annurev.ns.14.120164.001543|doi-access=|title=Chemistry of the Actinide Elements|year=1964|last1=Cunningham|first1=B. B.|journal=]|volume=14|pages=323–346|bibcode=1964ARNPS..14..323C}}</ref><ref name=":0">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.</ref> 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 ] form, the ] form, and the ] form.<ref name=":0" /><ref name=":4">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.</ref> Curium(III) oxide is either white or light tan in color and, while ] in ], is soluble in inorganic and ]s.<ref>{{cite book|author1=Norman M. Edelstein |author2=James D. Navratil |author3=Wallace W. Schulz |title=Americium and curium chemistry and technology|year=1984|publisher=D. Reidel Pub. Co.|pages=167–168}}</ref><ref name=":1">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.</ref> Its synthesis was first recognized in 1955.<ref name=":5">Morss, L. R., Fuger, J., Goffart, J. and R.G. Haire (1983). “Enthalpy of Formation and Magnetic Susceptibility of Curium Sesquioxide, Cm<sub>2</sub>0<sub>3</sub>.” ''Inorganic Chemistry'' (22)'':''1993-1996.</ref> |
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== Synthesis == |
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'''Curium oxide''' is a ] composed of ] and ]. Curium forms two ]s, ] ({{curium|2}}{{oxygen|3}}) and ] ({{curium}}{{oxygen|2}}). However, curium(III) oxide is more common. Both curium oxides are ]s, ] in ] but soluble in ]s. |
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{{manual|section|date=February 2023}} |
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Curium sesquioxide can be prepared in a variety of ways. |
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* Ignition with ]: Curium(III) oxalate is precipitated through a capillary tube. The precipitate is ignited by gaseous oxygen at 400 °C, and the resulting product is thermally ] via 600 °C and 10<sup>−4</sup> mm of pressure.<ref name=":2">Wallmann, J.C. (1964). “A Structural Transformation of Curium Sesquioxide.” ''Journal of Inorganic and Nuclear Chemistry'' (26): 2053-2057.</ref> |
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== External links == |
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* http://www.webelements.com/compounds/curium/dicurium_trioxide.html |
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* http://www.webelements.com/compounds/curium/curium_dioxide.html |
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* Aerosolized Curium Sesquioxide: The aerosolization process of Cm<sub>2</sub>O<sub>3</sub> can be done through multiple experimental processes. Typically, Cm<sub>2</sub>O<sub>3</sub> is aerosolized for experimental procedures which set out to discover the effects of curium metal within a biological system.<ref name=":1" /><ref name=":3">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 <sup>244</sup>Cm<sub>2</sub>0<sub>3</sub> in the Lung, Liver and Skeleton of F344 Rats and Comparison with <sup>239</sup>Pu0<sub>2</sub>.” ''Radiation Research'' (5): 598-612.</ref> |
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] |
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''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% <sup>244</sup>Cm, 8.4% <sup>243</sup>Cm, 3.9% other curium isotopes, and ~0.3% of the ], 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.<ref name=":1" /> NH<sub>3</sub>OH is then added to the purified curium nitrate, and the resulting precipitate is collected and rinsed with deionized water. The precipitate (Cm<sub>2</sub>O<sub>3</sub>) is resuspended in solvent and aerosolized with some sort of high output aerosol generator (ex: Lovelace ]).<ref name=":1" /> |
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{{inorganic-compound-stub}} |
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''Route 2:'' In other aerosolizations, instead of the addition of NH<sub>3</sub>OH 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.<ref name=":3" /> |
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* Reduction by Hydrogen Gas: A solution of curium trichloride is evaporated to dryness with pure nitric acid to produce curium nitrate. The curium nitrate is then ignited in air, producing curium oxide, believed to be an intermediate structure between CmO<sub>2</sub> and the formation of Cm<sub>2</sub>O<sub>3</sub>. The intermediate is scraped into capillary tubes attached to a vacuum system and reduced with gaseous hydrogen - the result of the combustion of UH<sub>3</sub>.<ref name=":2" /> |
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== Structure == |
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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.<ref name=":2" /> This transformation is undergone upon spontaneous <sup>244</sup>Cm alpha decay, which produces radiation damage effects within the cubic crystal lattice to distort it to that of hexagonal.<ref name=":0" /> 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.<ref name=":2" /> |
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== Crystallography == |
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The lattice parameters for three of the polymorphic structures of curium sesquioxide are given below. |
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<u>Hexagonal:</u> |
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] |
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{| class="wikitable" |
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!Data Table<ref name=":2" /><ref name=":7">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.</ref> |
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!Temperature (°C) |
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!Lengths of a (Å) |
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!Uncertainty (Å) |
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!Lengths of c (Å) |
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!Uncertainty (Å) |
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|1615 |
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|3.845 |
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|0.005 |
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|6.092 |
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|0.005 |
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| --* |
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|3.496 |
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|0.003 |
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|11.331 |
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|0.005 |
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(*: No specific temperature has been stated to produce the lengths listed in the second row.<ref name=":2" /><ref name=":7" />) |
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<u>Monoclinic:</u> |
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] |
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{| class="wikitable" |
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!Data Table<ref name=":8">Rimshaw, S. J., and E. E. Ketchen (1967). “Curium Data Sheets.” Oak Ridge National Laboratory - Union Carbide Corporation. pp. 42-102.</ref> |
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!Temperature (°C) |
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!Lengths of a (Å) |
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!Lengths of b (Å) |
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!Lengths of c (Å) |
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|- |
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|21 |
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|14.257** |
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|8.92** |
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|3.65** |
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(**: None of these lengths contained given uncertainties.<ref name=":8" />) |
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<u>Cubic:</u> |
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] |
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{| class="wikitable" |
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!Data Table<ref name=":2" /> |
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!Temperature (°C) |
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!Lengths of a (Å) |
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!Uncertainty (Å) |
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|21 |
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|10.97 |
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|0.01 |
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== Data == |
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Ever since the discovery (and isolation) of <sup>248</sup>Cm, the most stable curium isotope, experimental work on the thermodynamic properties of curium sesquioxide (and other curium compounds) has become more prevalent. However, <sup>248</sup>Cm can only be obtained in mg samples, so data collection for <sup>248</sup>Cm-containing compounds takes longer than that for compounds which predominantly contain other curium isotopes.<ref name=":0" /> 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 <sup>248</sup>Cm-compounds.<ref name=":0" /><ref name=":4" /><ref name=":5" /><ref name=":9">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.</ref><ref name=":10">Smith, Paul Kent (1969). “Melting Point of Curium Trioxide (Cm<sub>2</sub>O<sub>3</sub>).” ''Journal of Inorganic and Nuclear Chemistry'' (31): 241-245.</ref><ref name=":11">Smith, Paul Kent (1970). “High-Temperature Evaporation and Thermodynamic Properties of Cm<sub>2</sub>O<sub>3</sub>.” ''The Journal of Chemical Physics'' (52): 4964-4972.</ref> |
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{| class="wikitable" |
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!Ground State F-Configuration for Metal |
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!Approximate Melting Point (°C) |
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!'''Magnetic Susceptibility''' (μb) |
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!Uncertainty (μb) |
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!'''Enthalpy of Formation''' (kJ/mol) |
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!Uncertainty (kJ/mol) |
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!'''Average Standard Molar Entropy''' (J/molK) |
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!Uncertainty (J/molK) |
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|f<sup>7</sup> (Cm<sup>3+</sup>) |
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|2265* |
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|7.89** |
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|0.04** |
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| -400** |
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|5** |
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|157*** |
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|5*** |
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(*: 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.<ref name=":10" /><ref name=":11" />) |
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(**: Characteristic of the monoclinic form.) |
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(***: 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.<ref name=":9" />) |
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== Toxicology == |
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Curium metal is a ''']''' and emits ''']''' upon radioactive decay.<ref name=":9" /> Although it has a half life of 34 ms, many curium oxides, including curium sesquioxide, have half lives nearing thousands of years.<ref name=":5" /> 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.<ref>“Radionuclide Data Sheet: Curium.” University of California, San Diego. n.d.1.</ref> In one experiment, rats were introduced to aerosolized particulates of curium(III) oxide. Although the experiment proved that inhaled <sup>244</sup>Cm<sub>2</sub>O<sub>3</sub> is half as carcinogenic as compared to inhaled <sup>239</sup>PuO<sub>2</sub>, the rats still suffered from many biological deformities, such as skin lesions, malignant tumors, and lung neoplasms.<ref name=":3" /> 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.<ref name=":3" /> |
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== Applications == |
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Curium(III) oxide is heavily used in industrial grade-reactions and reagents.<ref name=":10" /> 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 ] and ] target substances.<ref name=":10" /> |
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== Other reactions == |
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Curium sesquioxide will spontaneously react with gaseous oxygen at high temperatures.<ref name=":7" /> 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.<ref name=":7" /> Curium sesquioxide has been shown to not react with nitrogen gas, spontaneously or non-spontaneously.<ref name=":7" /> |
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== See also == |
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* ] |
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== References == |
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<references /> |
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== External links == |
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{{Curium compounds}} |
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