Calculate the exact theoretical spin-only magnetic moment () for an isolated, gaseous divalent metal — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The neutral atom is Iron ($Fe, Z=26$), with configuration $[Ar] 3d^6 4s^2$. Ionizing to $Fe^{2+}$ removes the two $4s$ electrons, leaving $[Ar] 3d^6$. According to Hund's rule, a $d^6$ configuration contains exactly $n=4$ unpaired electrons. Using $\mu = \sqrt{n(n+2)}$, $\mu = \sqrt{4(6)} = \sqrt{24} \approx 4.89 \text{ B.M.}$