Which two transition metal ions has same 3d electronic configuration?

(A)    \(Mn^{3+}\)

(B)    \(Fe^{2+}\)

(C)    \(Mn^{2+}\)

(D)   \(Fe^{3+}\)

(E)    \(Cr^{3+}\)

Choose the correct answer from the options given below:

(C) and (D) only

The electronic configuration of the given compounds are :

(A) \(Mn^{3+}\)

The electronic configuration of \(Mn\) in the ground state is

\(_{25}Mn \longrightarrow _{18}Ar]\text{ }4s^2\text{ }3d^5\)

The electronic configuration of \(Mn\) in \(+3\) oxidation state is

\(Mn^{3+} \longrightarrow _{18}Ar]\text{ }4s^0\text{ }3d^4\)

(B) \(Fe^{2+}\)

The electronic configuration of \(Fe\) in the ground state is

\(_{26}Fe \longrightarrow _{18}Ar]\text{ }4s^2\text{ }3d^6\)

The electronic configuration of \(Fe\) in \(+2\) oxidation state is

\(Fe^{2+} \longrightarrow _{18}Ar]\text{ }4s^0\text{ }3d^6\)

(C) \(Mn^{2+}\)

The electronic configuration of \(Mn\) in the ground state is

\(_{25}Mn \longrightarrow _{18}Ar]\text{ }4s^2\text{ }3d^5\)

The electronic configuration of \(Mn\) in \(+2\) oxidation state is

\(Mn^{2+} \longrightarrow _{18}Ar]\text{ }4s^0\text{ }3d^5\)

(D) \(Fe^{3+}\)

The electronic configuration of \(Fe\) in the ground state is

\(_{26}Fe \longrightarrow _{18}Ar]\text{ }4s^2\text{ }3d^6\)

The electronic configuration of \(Fe\) in \(+3\) oxidation state is

\(Fe^{3+} \longrightarrow _{18}Ar]\text{ }4s^0\text{ }3d^5\)

(E) \(Cr^{3+}\)

The electronic configuration of \(Cr\) in the ground state is

\(_{24}Cr \longrightarrow _{18}Ar]\text{ }4s^1\text{ }3d^5\)

The electronic configuration of \(Cr\) in \(+3\) oxidation state is

\(Cr^{2+} \longrightarrow _{18}Ar]\text{ }4s^0\text{ }3d^3\)

From the above-given configurations, it is clear that both options (C) and (D) have the same \(3d\) configuration. Hence, the correct answer is (3) (C) and (D) only.