Question

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

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

Answer 1

Answer: (A)

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

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

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

Unpaired electron $(n)=0$; Diamagnetic