Chemistry - GENERAL CHEMISTRY Question with Solution | TestHub

Statement (A) is true: Fe³⁺ ($3d^5$) contains 5 unpaired electrons, whereas Fe²⁺ ($3d^6$) and Fe ($3d^{6}4s^2$) both contain only 4 unpaired electrons, giving Fe³⁺ the highest magnetic moment.

Statement (B) is false: Following Hund's rule gives Si ($3p^2$) 2 unpaired electrons (↑ ↑), while violating it pairs them up (↑ ↓), resulting in 0 unpaired electrons and different magnetic moments.

Statement (C) is true: The last electron of Mg enters the $3s$ orbital, where the quantum numbers are $n=3$, $\ell =0$, and $m_{\ell }=0$, so $n+\ell +m_{\ell }=3+0+0=3$.

Statement (D) is false: According to Slater's rules, the shielding constant ($\sigma$) for the $3s$ electron of Na is $8(0.85)+2(1.0)=8.8$, making $Z_{eff}=11-8.8=2.2$ (not 10.9).