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Hg2S is mercurous sulfide.
Mercurous has a charge of +2, and Oxide has a charge of -2. You cross the charges
and get Hg2O2. The 2s cancel out, leaving you : HgO
nuh uh, mercurOUS has a charge of +1, so it's Hg2O
mercurIC has a charge of +2, that would be HgO
Mercurous acetate is a salt.
The formula for mercurous chloride (Hg2Cl2). It is also called mercury(I) chloride.
HgNO3: mercurous nitrate is the earlier name for mercury (I) nitrate.