Which of the following element, has the highest number of unpaired electrons in it's ground state?
Which of the following element, has the highest number of unpaired electrons in it's ground state?
- $\mathrm{Mn}$
- $\mathrm{Cr}$
- $\mathrm{Ni}$
- $\mathrm{Fe}$
Solution
The electronic configurations of the given elements are as
$
\begin{aligned}
& { }_{25} \mathrm{Mn}=[\mathrm{Ar}] 3 d^5 4 s^2 \quad(\therefore 5 \text { unpaired electrons }) \\
& { }_{24} \mathrm{Cr}=[\mathrm{Ar}] 3 d^5 4 s^1 \quad(\therefore 6 \text { unpaired electrons }) \\
& { }_{28} \mathrm{Ni}=[\mathrm{Ar}] 3 d^8 4 s^2 \quad(\therefore 2 \text { unpaired electrons }) \\
& { }_{26} \mathrm{Fe}=[\mathrm{Ar}] 3 d^6 4 s^2 \quad(\therefore 4 \text { unpaired electrons }) \\
&
\end{aligned}
$
Hence, ${ }_{24} \mathrm{Cr}$ is having highest number of unpaired electrons i.e., 6
$
\text { Magnetic moment }=\sqrt{6(6+2)}=\sqrt{48}=6.92 \mathrm{BM}
$
(Highest magnetic moment)
Asked in: AP EAMCET 2021 (25 Aug Shift 1)
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