Question

The number of unpaired electrons in gaseous species of $Mn^{3+}$, $Cr^{3+}$ and $V^{3+}$ respectively are_____and the most stable species is_____.

• A. $4$, $3$ and $2$ ; $V^{3+}$
• B. $3$, $3$ and $2$ ; $Cr^{3+}$
• C. $4$, $3$ and $2$ ; $Cr^{3+}$
• D. $3$, $3$ and $3$ ; $Mn^{3+}$

Answer 1

Answer: (C)

$Mn^{3+} = 3d^4 = 4$ unpaired electrons, $Cr^{3+} = 3d^3 = 3 $ unpaired electrons, $V^{3+} = 3d^2 = 2$ unpaired electrons. $Cr^{3+}$ is most stable out of these in aqueous solution because it has half-filled tlg level (i.e., $t^3_{2g}$).