Q56 / 160 · JIPMER 2010 · Chemistry
The complex ion which has no $d$-electrons in the central metal atom is
- Correct answerA$\left[\mathrm{MnO}_4\right]^{-}$
- B$\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$
- C$\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}$
- D$\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}$
Solution
In $\left[\mathrm{MnO}_4\right]^{-}$, the oxidation state of Mn is +7 .
$\begin{aligned}
\mathrm{Mn}(25) & =[\mathrm{Ar}] 3 d^5 4 s^2 \\
\mathrm{Mn}^{7+} & =[\mathrm{Ar}]
\end{aligned}$
Thus, in $\left[\mathrm{MnO}_4\right]^{-}$no $d$-electron is present.
Hence, the correct answer is option: 'A'.