-ous -ic endings? Chemistry?

How do you know if something is supposed to habe an ous or ic ending? Like Hg2O ia Mercurous Oxide while HgO is Mercuric Oxide. I know it has something to do with valences or something but I don't understand what that 2 means or does.

1 Answer

  • Ian
    Lv 6
    7 years ago
    Favourite answer

    -ous, in this case, means mercury's in its 1 oxidation state, while -ic means it's in its 2 oxidation state.

    That '2' in the molecular formula simply means that the molecule contains 2 Hg atoms (subscripts apply to the elements on their left).

    Oxygen has an oxidation state of 2-. If it's taking two Hg atoms to balance that out, as in Hg2O, then they must each have an oxidation state of 1 .

    -2 2( 1) = 0

    If it takes just one Hg atom to balance out oxygen's 2- oxidation state, then that Hg atom is in its 2 oxidation state.

    -2 ( 2) = 0

    This same nomenclature and the related oxidation states applies to other metals like copper (cuprous (1 ) and cupric (2 ), but not to some other metals like iron (ferric (3 ) and ferrous (2 ))

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