This formula, if the compound exists, is the formula for mercury(I) peroxide. The formula for mercury(II) peroxide would be HgO2.
Hg2O2 is called Mercury peroxide because it is composed of two mercury (Hg) atoms and two peroxide (O2) ions. The peroxide ion consists of two oxygen atoms bonded together with a single bond, giving it the -1 charge. Therefore, the correct chemical formula for this compound is Hg2O2, reflecting the presence of peroxide ions rather than dioxide ions.
The formula for mercurous peroxide is Hg2O2.
Mercurous has a charge of +2, and Oxide has a charge of -2. You cross the chargesand get Hg2O2. The 2s cancel out, leaving you : HgOnuh uh, mercurOUS has a charge of +1, so it's Hg2OmercurIC has a charge of +2, that would be HgO