Question

Which one of the following ion exhibits d-d transition and paramagnetism as well?

• A. $Mn{O}_4^{-}$
• B. $C{r}_2{O}_7^{2-}$
• C. $Cr{O}_4^{2-}$
• D. $Mn{O}_4^{2-}$

Answer 1

Answer: (D)

As d-d transition and paramagnetism is possible in presence of unpaired $e^{-}$ , so here $Mn{O}_4^{2-}$ shows it.

$Cr{O}_4^{2-}\Rightarrow C{r}^{6+}=[Ar]$

Unpaired electron (n) = 0; Diamagnetic

$C{r}_2{O}_7^{2-}\Rightarrow C{r}^{6+}=[Ar]$

Unpaired electron (n) = 0; Diamagnetic

$Mn{O}_4^{2-}=M{n}^{6+}=[Ar]3d^1$

Unpaired electron (n) = 1; Paramagnetic

$Mn{O}_4^{-}=M{n}^{7+}=[Ar]3d^0$

Unpaired electron (n) = 0; Diamagnetic