Which of the following electronic configuration has associated magnetic moment of 4.89 B.M.?

Question

Professor PC Thomas Classes · Answer

$\mu = \sqrt{n(n+2)} = 4.89 \Rightarrow n \approx 4$. Configuration with 4 unpaired electrons matches $[\mathrm{Ar}]3\mathrm{d}^6$ (Fe$^{2+}$).