Copper wire is not an example of a pure element because although it's made by pure elements, it's not one itself. It's made by factories.
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Fe2O3 because O has a -2 charge and Fe and +3, you want the charges to equal each other so if you have 2 Fe with +3 charge the charge becomes 6 if you have 3 O with -2 charge the charge becomes 6.
