NEET Solved Paper 2018 Question 25
Question: Which one of the following ions exhibits d-d transition and paramagnetism as well? [NEET - 2018]
Options:
A) $ MnO_4^{-} $
B) $ C{r_2}O_7^{\text{2-}} $
C) $ CrO_4^{\text{2-}} $
D) $ MnO_4^{\text{2-}} $
Show Answer
Answer:
Correct Answer: D
Solution:
- $ CrO_4^{2-}\Rightarrow C{r^{6+}}=[Ar] $ Unpaired electron $ \text{(n)=0;} $
Diamagnetic $ C{r_2}O_7^{2-}\Rightarrow C{r^{6+}}=[Ar] $ Unpaired electron $ \text{(n)=0} $ ;
Diamagnetic $ MnO_4^{2-}=M{n^{6+}}=[Ar]3d^{1} $ Unpaired electron $ (n)=1 $
Paramagnetic $ MnO_4^{-}=M{n^{7+}}=[Ar] $ Unpaired electron $ (n)=0; $ Diamagnetic Hence, there is no d-d transition and no paramagnetism. Its colour is due to charge transfer spectra.
