A transition element is one which forms one or more stable ions which have partially filled d-orbitals. Manganese (Mn) could have an oxidation state of 7+, which means that it will lose all of the $\ce{3d^5}$ and $\ce{4s^2}$ electrons. So how could it make a 7+ ion in that case (which means that it will lose all of the $\ce{4s^2}$ and $\ce{3d^5}$ electrons) and still be defined as a transition element?
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$\begingroup$ It has plenty of other transition states too. Look back at your definition. $\endgroup$ – RobChem Mar 30 '15 at 22:38
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2$\begingroup$ It would be permanganate - it's impossible to have bare +7 cation, even +3 would be problematic - probably not really bare even if it would seem so. $\endgroup$ – Mithoron Mar 30 '15 at 22:49
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$\begingroup$ yeah i know that manganese has various states, does it depend to whats covalently bonded to manganese atom (how much of its outer electrons are shared).? $\endgroup$ – Abmon98 Mar 30 '15 at 22:50
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$\begingroup$ Yes, you're right. $\endgroup$ – Mithoron Mar 31 '15 at 22:23
The fact that manganese has a stable oxidation state in which it has (formally) lost all its $d$ electrons does not mean that it cannot be considered a transition metal, because it still has a lot of other oxidation states (like +II in $\ce{Mn^2+}$ or +VI in $\ce{MnO4^2-}$) with partially filled $d$ orbitals. Moreover, a naked $\ce{Mn^7+}$ ion does not exist in solution, it is only stable in the form of the oxocomplex $\ce{MnO4-}$.