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My textbook mentions that:

Iron is unable to be totally reduced... the most common non-zero oxidation states of iron is (o for oxidation, r for reduction) are: +2r, +3, +4o, +5o, +6o.

I thought it maybe meant going to $\ce{Fe^4+}$ (as the most reduced I commonly see is $\ce{Fe^3+}$), but then upon googling there is also $\ce{Fe^5+}$ ions, so how far does it have to go until it is totally reduced (if this is even what it meant by totally reduced)? Edit: Sorry, got reduction and oxidation mixed up (thanks for pointing this out DVSA). However, my question still stands, though replacing the above with more to e.g. $\ce{Fe^4-}$ than $\ce{Fe^3-}$ .

The question, for context, is below (I have already typed up what I think are the relevant parts above). FYI the answer is D, but I want to know what B means. enter image description here

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    $\begingroup$ Sounds fishy to me - iron can be reduced to $\ce{Fe^0}$, even though it is reactive is aqueous/oxygen-rich environments. From Wikipedia: "Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen and water. Fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. " $\endgroup$ – Todd Minehardt Nov 12 '16 at 20:47
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    $\begingroup$ Thanks Todd. You were right it was a fishy statement and a misleading question from me. See comment on DSVA's answers. $\endgroup$ – K-Feldspar Nov 12 '16 at 21:46
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Reduction means that electrons are added, you are talking about oxidation. I haven't heared the term "fully reduced" in this context before, but I guess it means a full shell. In case of iron this would mean a oxidation state of -10, while as far as I know the highest we can get is -4.

And don't confuse oxidation states with charge of ions.

Well, now that I see the actual question I think there's nothing to really understand here. Just a wrong, made up answer.

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  • $\begingroup$ Oh. I assumed that the wrong part was that "Scandium is similiar too", rather than "Iron being unable to be totally reduced". Thank you for spotting my error. $\endgroup$ – K-Feldspar Nov 12 '16 at 21:44

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