Chemistry - Complete d-block Question with Solution | TestHub

For $d$ -block elements, oxidation state $=ns$ electrons $+(n-1)d$ electrons (unpaired) (a) $\mathrm{Mn}(25)=[\mathrm{Ar}]3d^{5}4s^2$ $$\text{ O. }\mathrm{S}.=5+2=7$$ (b) $\mathrm{Cr}(24)=[\mathrm{Ar}]3d^{5}4s^1$ O. S. $=5+1=6$ (c) $\mathrm{Cu}(29)=[\mathrm{Ar}]3d^{10}4s^1$ O. S. $=0+1=1$ (d) $\mathrm{Fe}(26)=[\mathrm{Ar}]3d^{6}4s^2$ O.S. $=+2$ and $+3$ Thus, only Mn exhibits $+7$ oxidation state among the given elements.