The dand fblock elements - Result Question 3
####3. Which one of the following ions exhibits $d-d$ transition and paramagnetism as well? [2018]
(a) $CrO_4^{2-}$
(b) $Cr_2 O_7^{2-}$
(c) $MnO_4^{2-}$
(d) $MnO_4^{-}$
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Solution:
(c) $CrO_4^{2-} \quad Cr^{6+}$ diamagnetic
$Cr_2 O_7^{2-} \quad Cr^{6+}$ diamagnetic
$MnO_4^{-} \quad Mn^{7+}$ diamagnetic
$MnO_4^{2-} \quad Mn^{6+}$ paramagnetic
Thus, unpaired electron is present, so $d-d$ transition is possible.
For tetrahedral geometry:
