Question

Which one of the following ions has electronic configuration $[Ar] 3d^6 ? $
(At.no. $Mn =25, Fe = 26,Co =27, Ni = 28)$

• A. $Ni^{3+} $
• B. $Mn^{3+} $
• C. $Fe^{3+} $
• D. $Co^{3+} $

Answer 1

Answer: (D)

$Ni^{3+}(28)=[Ar]3d^7 $
$Mn^{3+}(25)=[Ar]3d^4 $
$Fe^{3+}(26)=[Ar]3d^5 $
$Co^{3+}(27)=[Ar]3d^6 $
Hence, $Co^{3+} $ has $ 3d^6 $ electronic configuration