Plutonium trioxide is an inorganic compound of plutonium and oxygen with the chemical formula PuO3. 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.

Theoretical calculations on molecular actinide trioxides predict that while molecular plutonium trioxide should attain the +6 oxidation state for plutonium, the molecular trioxides of the heavier actinides should be regarded as having the actinide in the +5 oxidation state

Synthesis

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

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. 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:

2PuO3·xH2O → 2PuO2 + O2 + 2xH2O

Dissolves in acids, forming salts:

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