Plutonium compounds

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Various oxidation states of plutonium in solution Plutonium in solution.jpg
Various oxidation states of plutonium in solution

Plutonium compounds are compounds containing the element plutonium (Pu). At room temperature, pure plutonium is silvery in color but gains a tarnish when oxidized. [1] The element displays four common ionic oxidation states in aqueous solution and one rare one: [2]

Contents

The color shown by plutonium solutions depends on both the oxidation state and the nature of the acid anion. [4] It is the acid anion that influences the degree of complexing—how atoms connect to a central atom—of the plutonium species. Additionally, the formal +2 oxidation state of plutonium is known in the complex [K(2.2.2-cryptand)] [PuIICp″3], Cp″ = C5H3(SiMe3)2. [5]

A +8 oxidation state is possible as well in the volatile tetroxide PuO
4. [6] Though it readily decomposes via a reduction mechanism similar to FeO
4, PuO
4 can be stabilized in alkaline solutions and chloroform. [7] [6]

Metallic plutonium is produced by reacting plutonium tetrafluoride with barium, calcium or lithium at 1200 °C. [8] Metallic plutonium is attacked by acids, oxygen, and steam but not by alkalis and dissolves easily in concentrated hydrochloric, hydroiodic and perchloric acids. [9] Molten metal must be kept in a vacuum or an inert atmosphere to avoid reaction with air. [9] At 135 °C the metal will ignite in air and will explode if placed in carbon tetrachloride. [10]

Plutonium pyrophoricity can cause it to look like a glowing ember under certain conditions. Plutonium pyrophoricity.jpg
Plutonium pyrophoricity can cause it to look like a glowing ember under certain conditions.
Twenty micrograms of pure plutonium hydroxide 96602765.lowres.jpeg
Twenty micrograms of pure plutonium hydroxide

Plutonium is a reactive metal. In moist air or moist argon, the metal oxidizes rapidly, producing a mixture of oxides and hydrides. [11] If the metal is exposed long enough to a limited amount of water vapor, a powdery surface coating of PuO2 is formed. [11] Also formed is plutonium hydride but an excess of water vapor forms only PuO2. [9]

Plutonium shows enormous, and reversible, reaction rates with pure hydrogen, forming plutonium hydride. [12] It also reacts readily with oxygen, forming PuO and PuO2 as well as intermediate oxides; plutonium oxide fills 40% more volume than plutonium metal. The metal reacts with the halogens, giving rise to compounds with the general formula PuX3 where X can be F, Cl, Br or I and PuF4 is also seen. The following oxyhalides are observed: PuOCl, PuOBr and PuOI. It will react with carbon to form PuC, nitrogen to form PuN and silicon to form PuSi2. [2] [10]

The organometallic chemistry of plutonium complexes is typical for organoactinide species; a characteristic example of an organoplutonium compound is plutonocene. [13] [14] Computational chemistry methods indicate an enhanced covalent character in the plutonium-ligand bonding. [12] [14]

Powders of plutonium, its hydrides and certain oxides like Pu2O3 are pyrophoric, meaning they can ignite spontaneously at ambient temperature and are therefore handled in an inert, dry atmosphere of nitrogen or argon. Bulk plutonium ignites only when heated above 400 °C. Pu2O3 spontaneously heats up and transforms into PuO2, which is stable in dry air, but reacts with water vapor when heated. [15]

Crucibles used to contain plutonium need to be able to withstand its strongly reducing properties. Refractory metals such as tantalum and tungsten along with the more stable oxides, borides, carbides, nitrides and silicides can tolerate this. Melting in an electric arc furnace can be used to produce small ingots of the metal without the need for a crucible. [9]

Cerium is used as a chemical simulant of plutonium for development of containment, extraction, and other technologies. [16]

See also

Notes

  1. ↑ The PuO+
    2     ion is unstable in solution and will disproportionate into Pu4+ and PuO2+
    2    ; the Pu4+ will then oxidize the remaining PuO+
    2     to PuO2+
    2    , being reduced in turn to Pu3+. Thus, aqueous solutions of PuO+
    2     tend over time towards a mixture of Pu3+ and PuO2+
    2    . UO+
    2     is unstable for the same reason. [3]

Related Research Articles

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

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

The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. 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 transuranic radioactive chemical element with the 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 transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This 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">Neptunium</span> Chemical element, symbol Np and atomic number 93

Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus. A neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. Neptunium metal is silvery and tarnishes when exposed to air. The element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. It is radioactive, poisonous, pyrophoric, and capable of accumulating in bones, which makes the handling of neptunium dangerous.

<span class="mw-page-title-main">Redox</span> Chemical reaction in which oxidation states of atoms are changed

Redox is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state.

In chemistry, a reducing agent is a chemical species that "donates" an electron to an electron recipient. Examples of substances that are commonly reducing agents include the Earth metals, formic acid, oxalic acid, and sulfite compounds.

A substance is pyrophoric if it ignites spontaneously in air at or below 54 °C (129 °F) or within 5 minutes after coming into contact with air. Examples are organolithium compounds and triethylborane. Pyrophoric materials are often water-reactive as well and will ignite when they contact water or humid air. They can be handled safely in atmospheres of argon or nitrogen. Class D fire extinguishers are designated for use in fires involving pyrophoric materials. A related concept is hypergolicity, in which two compounds spontaneously ignite when mixed.

Silane is an inorganic compound with chemical formula, SiH4. It is a colourless, pyrophoric, toxic gas with a sharp, repulsive smell, somewhat similar to that of acetic acid. Silane is of practical interest as a precursor to elemental silicon. Silane with alkyl groups are effective water repellents for mineral surfaces such as concrete and masonry. Silanes with both organic and inorganic attachments are used as coupling agents.

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

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. Curium trioxide can exist as five polymorphic forms. 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. Curium(III) oxide is either white or light tan in color and, while insoluble in water, is soluble in inorganic and mineral acids. Its synthesis was first recognized in 1955.

Plutonium hydride is a non-stoichiometric chemical compound with the formula PuH2+x. It is one of two characterised hydrides of plutonium, the other is PuH3. PuH2 is non-stoichiometric with a composition range of PuH2 – PuH2.7. Additionally metastable stoichiometries with an excess of hydrogen (PuH2.7 – PuH3) can be formed. PuH2 has a cubic structure. It is readily formed from the elements at 1 atmosphere at 100–200 °C: When the stoichiometry is close to PuH2 it has a silver appearance, but gets blacker as the hydrogen content increases, additionally the color change is associated with a reduction in conductivity.

Uranium compounds are compounds formed by the element uranium (U). Although uranium is a radioactive actinide, its compounds are well studied due to its long half-life and its applications. It usually forms in the +4 and +6 oxidation states, although it can also form in other oxidation states.

<span class="mw-page-title-main">Organoactinide chemistry</span> Study of chemical compounds containing actinide-carbon bonds

Organoactinide chemistry is the science exploring the properties, structure and reactivity of organoactinide compounds, which are organometallic compounds containing a carbon to actinide chemical bond.

<span class="mw-page-title-main">Plutonium</span> Chemical element, symbol Pu and atomic number 94

Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous.

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

The oxidation state of oxygen is −2 in almost all known compounds of oxygen. The oxidation state −1 is found in a few compounds such as peroxides. Compounds containing oxygen in other oxidation states are very uncommon: −1⁄2 (superoxides), −1⁄3 (ozonides), 0, +1⁄2 (dioxygenyl), +1, and +2.

Uranium hydride, also called uranium trihydride (UH3), is an inorganic compound and a hydride of uranium.

<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.

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.

Neptunium compounds are compounds containg the element neptunium (Np). Neptunium has five ionic oxidation states ranging from +3 to +7 when forming chemical compounds, which can be simultaneously observed in solutions. It is the heaviest actinide that can lose all its valence electrons in a stable compound. The most stable state in solution is +5, but the valence +4 is preferred in solid neptunium compounds. Neptunium metal is very reactive. Ions of neptunium are prone to hydrolysis and formation of coordination compounds.

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.

References

  1. ↑ Heiserman, David L. (1992). "Element 94: Plutonium" . Exploring Chemical Elements and their Compounds. New York (NY): TAB Books. pp.  339. ISBN   0-8306-3018-X.
  2. 1 2 Lide, David R., ed. (2006). Handbook of Chemistry and Physics (87th ed.). Boca Raton: CRC Press, Taylor & Francis Group. pp. 4–27. ISBN   0-8493-0487-3.
  3. ↑ Crooks, William J. (2002). "Nuclear Criticality Safety Engineering Training Module 10 – Criticality Safety in Material Processing Operations, Part 1" (PDF). Archived from the original (PDF) on March 20, 2006. Retrieved February 15, 2006.
  4. ↑ Matlack, George (2002). A Plutonium Primer: An Introduction to Plutonium Chemistry and its Radioactivity. Los Alamos National Laboratory. LA-UR-02-6594.
  5. ↑ Windorff, Cory J.; Chen, Guo P; Cross, Justin N; Evans, William J.; Furche, Filipp; Gaunt, Andrew J.; Janicke, Michael T.; Kozimor, Stosh A.; Scott, Brian L. (2017). "Identification of the Formal +2 Oxidation State of Plutonium: Synthesis and Characterization of {PuII[C5H3(SiMe3)2]3}−". J. Am. Chem. Soc. 139 (11): 3970–3973. doi:10.1021/jacs.7b00706. PMID   28235179.
  6. 1 2 Zaitsevskii, Andréi; Mosyagin, Nikolai S.; Titov, Anatoly V.; Kiselev, Yuri M. (21 July 2013). "Relativistic density functional theory modeling of plutonium and americium higher oxide molecules". The Journal of Chemical Physics. 139 (3): 034307. Bibcode:2013JChPh.139c4307Z. doi:10.1063/1.4813284. PMID   23883027.
  7. ↑ Kiselev, Yu. M.; Nikonov, M. V.; Dolzhenko, V. D.; Ermilov, A. Yu.; Tananaev, I. G.; Myasoedov, B. F. (17 January 2014). "On existence and properties of plutonium(VIII) derivatives". Radiochimica Acta. 102 (3): 227–237. doi:10.1515/ract-2014-2146. S2CID   100915090.
  8. ↑ Eagleson, Mary (1994). Concise Encyclopedia Chemistry . Berlin: Walter de Gruyter. p. 840. ISBN   978-3-11-011451-5.
  9. 1 2 3 4 Miner, William N.; Schonfeld, Fred W. (1968). "Plutonium" . In Clifford A. Hampel (ed.). The Encyclopedia of the Chemical Elements. New York (NY): Reinhold Book Corporation. pp.  540–546. LCCN   68029938.
  10. 1 2 Emsley, John (2001). "Plutonium". Nature's Building Blocks: An A–Z Guide to the Elements. Oxford (UK): Oxford University Press. pp. 324–329. ISBN   0-19-850340-7.
  11. 1 2 "Plutonium, Radioactive". Wireless Information System for Emergency Responders (WISER). Bethesda (MD): U.S. National Library of Medicine, National Institutes of Health. Archived from the original on August 22, 2011. Retrieved November 23, 2008. (public domain text)
  12. 1 2 Hecker, Siegfried S. (2000). "Plutonium and its alloys: from atoms to microstructure" (PDF). Los Alamos Science. 26: 290–335. Archived (PDF) from the original on February 24, 2009. Retrieved February 15, 2009.
  13. ↑ Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Oxford (UK): Butterworth-Heinemann. p. 1259. ISBN   0-7506-3365-4.
  14. 1 2 Apostolidis, Christos; Walter, Olaf; Vogt, Jochen; Liebing, Phil; Maron, Laurent; Edelmann, Frank T. (2017). "A Structurally Characterized Organometallic Plutonium(IV) Complex". Angewandte Chemie International Edition. 56 (18): 5066–5070. doi:10.1002/anie.201701858. ISSN   1521-3773. PMC   5485009 . PMID   28371148.
  15. ↑ "Primer on Spontaneous Heating and Pyrophoricity – Pyrophoric Metals – Plutonium". Washington (DC): U.S. Department of Energy, Office of Nuclear Safety, Quality Assurance and Environment. 1994. Archived from the original on April 28, 2007.
  16. ↑ Crooks, W. J.; et al. (2002). "Low Temperature Reaction of ReillexTM HPQ and Nitric Acid". Solvent Extraction and Ion Exchange. 20 (4–5): 543–559. doi:10.1081/SEI-120014371. S2CID   95081082. Archived from the original on June 14, 2011. Retrieved January 24, 2010.
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