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What is the sum of all the oxidation numbers in any compound?
In any compound the sum of the is equal to the charge on the compound.
And of course if the compound is neutral, then the sum of the oxidation numbers of is neutral. If the compound is an ion, i.e. ##CrO_4^(2-), NO_3^-, SO_4^(2-)##, the sum of the oxidation numbers is the charge on the ion.
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