Trioxide

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.

MO3

 * 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

M2O3

 * 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

Other trioxides

 * Mineral trioxide aggregate
 * Sulfur trioxide pyridine complex, SO3(py)