Question

Which of the following is the correct order for the theoretical magnetic moment?

• A. ${Cr}^{3+}>{Mn}^{2+}={Fe}^{3+}$
• B. ${Cr}^{3+}={Mn}^{2+}<{Fe}^{3+}$
• C. ${Cr}^{3+}<{Mn}^{2+}={Fe}^{3+}$
• D. ${Cr}^{3+}<{Mn}^{2+}<{Fe}^{3+}$

Answer 1

The correct option is C ${Cr}^{3+}<{Mn}^{2+}={Fe}^{3+}$

$F{e}^{3+}\Rightarrow \left[Ar\right]4s^{0}3d^5$

$M{n}^{2+}\Rightarrow \left[Ar\right]4s^{0}3d^5$

$C{r}^{3+}\Rightarrow \left[Ar\right]4s^{0}3d^3$

Magnetic moment of ${Mn}^{2+}={Fe}^{3+}$ as both have same no. of valence $e^{-}$, 5 and $C{r}^{3+}$ has $3$ valence. $e^{-}$ which is less than ${Mn}^{2+}$ and ${Fe}^{3+}$ which is $5$. So comparatively, $C{r}^{3+}$ will have less magnetic moment than ${Mn}^{2+}$ and ${Fe}^{3+}$.
Option C is correct.