Oxidation state of iron ions in a unit cell

[![enter image description here](https://i.stack.imgur.com/Qiqtw.png)](https://i.stack.imgur.com/Qiqtw.png)



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> Consider UC (unit cell) for a cubic ionic lattice containing 4 oxide ions - what is the avg oxidation state for Fe ions in this lattice? 
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The four oxide ions create a -8 charge that must be counteracted by the iron ions. In a FCC unit cell, there are 3 total Fe ions per UC; therefore each ion must have a +8/3rds oxidation state. 


Is this correct? 


