Fe2O3
The chemical formula for iron (III) oxide is Fe2O3, where Fe represents iron and O represents oxygen.
Iron(II) oxide is Fe(OH)2 Iron(III) oxide is Fe(OH)3
Its difficult to understand your question, I can make an assumption (although your stoichiometry is off). Are you asking about Iron Oxide compounds? Iron is a transition metal, abbreviated "Fe." It has two oxidative states, +2 and +3--often written as Fe (II) and Fe (III). If you have Fe(II) oxide, FeO, it would be called "ferrous oxide." If you have Fe(III) oxide, Fe2 O3, it would be called "ferric oxide." The other forms in your question aren't correct and I cannot answer them.
There are a number of chemical compounds conmade up from iron and oxygenIron(III) oxide, ferric oxide, is Fe2O3Iron(II)oxide, ferrous oxide, FeOiron(II,III) oxide, ferrous ferric oxide, Fe3O4
FeO for ferrous oxide, ( iron(II) oxide); Fe2O3 for ferric oxide, (iron(III) oxide) and Fe3O4 for ferrous ferric oxide, (iron (II,III) oxide)
Fe2O3 is the chemical formula for iron(III) oxide, also known as rust. It is a reddish-brown compound that forms when iron reacts with oxygen in the presence of moisture. Iron(III) oxide is commonly found on rusted metal surfaces.
The oxidation number of iron in ferrousofericoxide (Fe3O4) is a combination of Fe(II) and Fe(III) ions. The Fe(II) ions have an oxidation number of +2, while the Fe(III) ions have an oxidation number of +3. Each formula unit of Fe3O4 contains two Fe(III) ions and one Fe(II) ion, resulting in an average oxidation number of +2.67 for iron in this compound.
Phosphorus(III) oxide has the formula P2O3 but it exists as the molecule of P4O6
Fe-Iron OH-hydroxide ironic hydroide
The chemical formula for manganese(III) oxide is Mn2O3.
If it existed the formula would be Cu2O3
FeO for ferrous oxide, ( iron(II) oxide); Fe2O3 for ferric oxide, (iron(III) oxide) and Fe3O4 for ferrous ferric oxide, (iron (II,III) oxide)