What is Uranium trioxide?
{{chembox | Watchedfields = changed | verifiedrevid = 452010868 | Name = Uranium trioxide | ImageFile = UO3 gamma lattice.png | IUPACName = Uranium trioxide<br/>Uranium(VI) oxide | OtherNames = Uranyl oxide<br/>Uranic oxide |Section1={{Chembox Identifiers | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 1344-58-7 }} |Section2={{Chembox Properties | Formula = UO<sub>3</sub> | MolarMass = 286.29 g/mol | Density = 5.5–8.7 g/cm<sup>3</sup> | Appearance = yellow-orange powder | Solubility = Partially soluble | MeltingPt = ~200–650&nbsp;°C (decomposes) }} |Section3={{Chembox Structure | CrystalStruct = ''see text'' | SpaceGroup = ''I''4<sub>1</sub>/amd (''γ''-UO<sub>3</sub>) | Coordination = }} |Section4={{Chembox Thermochemistry | DeltaHf = −1230&nbsp;kJ·mol<sup>−1</sup><ref name=b1>{{cite book| author = Zumdahl, Steven S.|title =Chemical Principles 6th Ed.| url = https://archive.org/details/chemicalprincipl0000zumd_u9g0| publisher = Houghton Mifflin Company| year = 2009| isbn = 978-0-618-94690-7|page=A23}}</ref> | Entropy = 99&nbsp;J·mol<sup>−1</sup>·K<sup>−1</sup><ref name=b1/> }} |Section7={{Chembox Hazards | ExternalSDS = [http://www.ibilabs.com/UO3-MSDS.htm External MSDS] | EUClass = Very toxic ('''T+''')<br/>Dangerous for the environment ('''N''') | RPhrases = {{R26/28}}, {{R33}}, {{R51/53}} | SPhrases = {{S1/2}}, {{S20/21}}, {{S45}}, {{S61}} | NFPA-H = 4 | NFPA-F = 0 | NFPA-R = 1 | NFPA-S = RA | FlashPt = Non-flammable | LD50 = | PEL = }} |Section8={{Chembox Related | OtherAnions = | OtherFunction = [[Uranium dioxide]]<br/>[[Triuranium octoxide]] | OtherFunction_label = [[uranium]] [[oxide]]s | OtherCompounds = }} }} '''Uranium trioxide (UO<sub>3</sub>)''', also called '''[[uranyl]] oxide''', '''uranium(VI) oxide''', and '''uranic oxide''', is an [[oxide]] of [[uranium]]. UO<sub>3</sub> is a hexavalent oxide, which means that the uranium in the compound has an [[oxidation state]] of +6. It can be formed by heating [[uranyl nitrate]] to 400&nbsp;°C. UO<sub>3</sub> is a poisonous and slightly [[radioactive]]