Trioxide
{{Short description|Compound with three oxygen atoms}}
{{For|the triple-oxygen-molecule existing in the atmosphere|Ozone}}
A trioxide is a compound with three oxygen atoms. For metals with the M2O3 formula there are several common structures. Al2O3, Cr2O3, Fe2O3, and V2O3 adopt the corundum structure. Many rare earth oxides adopt the "A-type rare earth structure" which is hexagonal. Several others plus indium oxide adopt the "C-type rare earth structure", also called "bixbyite", which is cubic and related to the fluorite structure.{{cite book|last=Jaffe|first=Howard W.|title=Crystal Chemistry and Refractivity|year=1996|publisher=Courier Dover Publications|isbn=978-0-486-69173-2|pages=266–272|url=https://books.google.com/books?id=lbxUYhC5YEEC&dq=bixbyite+crystal+structure&pg=PA274|access-date=2021-12-05|archive-date=2023-09-08|archive-url=https://web.archive.org/web/20230908040812/https://books.google.com/books?id=lbxUYhC5YEEC&dq=bixbyite+crystal+structure&pg=PA274|url-status=live}}
List of trioxides
=MO<sub>3</sub>=
- Carbon trioxide, CO3
- Chromium trioxide, CrO3
- Molybdenum trioxide, MoO3
- Rhenium trioxide, ReO3
- Selenium trioxide, SeO3
- Sulfur trioxide, SO3
- Tellurium trioxide, TeO3
- Tungsten trioxide, WO3
- Uranium trioxide, UO3
- Xenon trioxide, XeO3
=M<sub>2</sub>O<sub>3</sub>=
- Antimony trioxide, Sb2O3
- Arsenic trioxide, As2O3
- Bismuth(III) oxide, Bi2O3
- Boron trioxide, B2O3
- Cobalt(III) oxide, Co2O3
- Dichlorine trioxide, Cl2O3
- Dinitrogen trioxide, N2O3
- Gadolinium oxide, Gd2O3
- Gallium(III) oxide, Ga2O3
- Gold trioxide, Au2O3
- Indium(III) oxide, In2O3
- Iron(III) oxide, Fe2O3
- Manganese(III) oxide, Mn2O3
- Nickel(III) oxide, Ni2O3
- Phosphorus trioxide, P4O6 (named before the true formula known)
- Thallium(III) oxide, Tl2O3
- Terbium(III) oxide, Tb2O3
- Trioxidane, H2O3
- Vanadium trioxide, V2O3
- Ytterbium(III) oxide, Yb2O3
- Yttrium(III) oxide, Y2O3