Correct option is (2) 3
\( {\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{+2} \rightarrow \mathrm{d}^6 \mathrm{WFL} \rightarrow \mathrm{t}_{2 \mathrm{~g}}^4 \mathrm{eg}^2 \text { (even no of } \mathrm{e}^{-} \text {in } \mathrm{t}_{2 \mathrm{~g}} \text { ) }}\)
\({\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{+2} \mathrm{~d}^7 \rightarrow \mathrm{WFL} \rightarrow \mathrm{t}_{2 \mathrm{~g}}^5 \mathrm{eg}^2 \text { (odd no of } \mathrm{e}^{-} \text {in } \mathrm{t}_{2 \mathrm{~g}} \text { ) }} \)
\({\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{+3} \rightarrow \mathrm{d}^6 \mathrm{SFL} \rightarrow \mathrm{t}_{2 \mathrm{~g}}^6 \mathrm{eg}^{\circ} \text { (even no of } \mathrm{e}^{-} \text {in } \mathrm{t}_{2 \mathrm{~g}} \text { ) }} \)
\({\left[\mathrm{Cu}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{+2} \mathrm{~d}^4 \rightarrow \text { WFL t }_{2 \mathrm{~g}}^6 \mathrm{eg}^3 \text { (even no e } \mathrm{e}^{-} \text {in } \mathrm{t}_{2 \mathrm{~g}} \text { ) }}\)
\({\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{+2} \mathrm{~d}^4 \rightarrow \text { WFL t }_{2 \mathrm{~g}}^3 \mathrm{eg}^1 \text { (odd no of } \mathrm{e}^{-} \text {in } \mathrm{t}_{2 \mathrm{~g}} \text { ) }} \)
Thus three complex show even no of \(e^-\) in \(t_{2g}\) orbital.
