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Calculate the oxidation number of $\ce{Fe}$ in $\ce{Fe2O3}$.

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Alright. So we have a metal and an non metal. This means that iron will lose electrons and give them to oxygen. So it will be a positive oxidation number for iron I guess.

The question is, how much? A wild guess is $2+$ because, well, each iron would is bound to two oxygens so I imagine each oxygen will take one electron each?

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  • $\begingroup$ The compound you are trying to assign oxidation numbers to is not covalent. The structure you posted is not correct. For the charges of the involved ions, ask yourself which element is most electronegative, how many electrons does it need for an octet (=charge), where do the electrons come from, what is the resulting charge for this element. $\endgroup$ – Martin - マーチン Jul 16 '15 at 8:50
  • $\begingroup$ Also related: chemistry.stackexchange.com/q/10944/4945 $\endgroup$ – Martin - マーチン Jul 16 '15 at 8:53
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Oxidation number of Fe is +3. This is because oxygen has a charge of -2. There are 3 oxygen atoms. So net charge becomes -6. Thus to balance it, each of the 2 Fe atoms must have a charge of +3 (-6 + 6 = 0).

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