What Is The Chemical Formula For Silver(I,III) Oxide?

There is no such compound as silver(I,III) oxide.

Silver can exist in two oxidation states: +1 and +3. The oxide of silver in the +1 oxidation state is silver(I) oxide, which has the chemical formula Ag2O. The oxide of silver in the +3 oxidation state is silver(III) oxide, which has the chemical formula Ag2O3.

It is not possible for silver to simultaneously exist in both the +1 and +3 oxidation states in a single compound. Therefore, there is no such thing as silver(I,III) oxide.