Which one of the following ions has electronic configuration $[\mathrm{Ar}] 3 \mathrm{~d}^6$ ? (At. no:…
Which one of the following ions has electronic configuration $[\mathrm{Ar}] 3 \mathrm{~d}^6$ ?
(At. no: $\mathrm{Mn}=25, \mathrm{Fe}=26, \mathrm{Co}=27, \mathrm{Ni}=28$ )
$\mathrm{Ni}^{3+}$
$\mathrm{Mn}^{3+}$
$\mathrm{Fe}^{3+}$
$\mathrm{Co}^{3+}$
Solution
Key Idea Write the electronic configurations of given ions and find the correct answer.
$\begin{aligned}
\mathrm{Ni}^{3+}(28) & =[\mathrm{Ar}] 3 \mathrm{~d}^7 \\
\mathrm{Mn}^{3+}(25) & =[\mathrm{Ar}] 3 \mathrm{~d}^4 \\
\mathrm{Fe}^{3+}(26) & =[\mathrm{Ar}] 3 \mathrm{~d}^5 \\
\mathrm{Co}^{3+}(27) & =[\mathrm{Ar}] 3 \mathrm{~d}^6
\end{aligned}$