Plutonium trioxide

Plutonium trioxide

Names
Other names Plutonium(VI) oxide
Identifiers
CAS Number	12311-78-3  N
Properties
Chemical formula	PuO3
Molar mass	536 g·mol−1
Appearance	golden-red crystals (hydrates)
Solubility in water	insoluble (hydrates)
Related compounds
Other anions	Uranium trioxide Neptunium trioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Plutonium trioxide is an inorganic compound of plutonium and oxygen with the chemical formula PuO₃. ^[1] This is a high-order oxide of plutonium where the metal is in the +6 oxidation state. The compound is less stable and less common than the common plutonium dioxide PuO₂.

The oxidation state of (VI) for actinides is attained exclusively in plutonium trioxide, while in heavier actinides, the T-shaped trioxide molecules are better described as having a pentavalent oxidation state. ^[2]

Synthesis

Initialy, plutonium(III) hydroxide is obtained, which then transforms into plutonium(IV) hydroxide in air, and then oxygen containing ozone is passed through the suspension: ^[3]

Pu(OH)₄ + O₃ → PuO₃·H₂O + O₂ + H₂O

Physical properties

Plutonium trioxide forms hydrates of variable composition PuO₃•xH₂O, where x = 0.8–1, which are golden-red crystals. ^[4] Not isolated in the anhydrous state: it decomposes when attempted to separate the water. When stored in the air, the compound absorbs moisture up to the composition of PuO₃•H₂O. Insoluble in water.

Chemical properties

Decomposes when heated: ^[5]

2PuO₃·xH₂O → 2PuO₂ + O₂ + 2xH₂O

Dissolves in acids, forming salts:

PuO₃·xH₂O + 2HNO₃ → PuO₂(NO₃)₂ + (x + 1)·H₂O

References

1. May, Iain; Bryan, N. D.; Alvares, Rebeca (31 October 2007). Recent Advances In Actinide Science. Royal Society of Chemistry. p. 275. ISBN   978-1-84755-536-6 . Retrieved 11 January 2026.
2. Zaitsevskii, Andréi (14 October 2015). "Plutonium and transplutonium element trioxides: molecular structures, chemical bonding, and isomers". Physical Chemistry Chemical Physics . 17 (38): 24831–24836. doi:10.1039/c5cp02190a. ISSN   1463-9084 . Retrieved 11 January 2026.
3. Bagnall, K. W.; Laidler, J. B. (1 January 1964). "516. Neptunium and plutonium trioxide hydrates". Journal of the Chemical Society (Resumed) (0): 2693–2696. doi:10.1039/JR9640002693. ISSN   0368-1769 . Retrieved 11 January 2026.
4. Lemire, Robert J. (26 August 2001). Chemical Thermodynamics of Neptunium and Plutonium. Elsevier. p. 339. ISBN   978-0-444-50379-4 . Retrieved 11 January 2026.
5. Structural Chemistry of Inorganic Actinide Compounds. Amsterdam; Oxford: Elsevier. 2007. p. 491. ISBN   978-0-444-52111-8 . Retrieved 11 January 2026.