Question
The number of unpaired electrons in gaseous species of $$M{n^{3 + }},C{r^{3 + }}$$ and $${V^{3 + }}$$ respectively are ______ and the most stable species is ______ .
A.
4, 3 and 2 ; $${V^{3 + }}$$
B.
3, 3 and 2 ; $$C{r^{3 + }}$$
C.
4, 3 and 2 ; $$C{r^{3 + }}$$
D.
3, 3 and 3 ; $$M{n^{3 + }}$$
Answer :
4, 3 and 2 ; $$C{r^{3 + }}$$
Solution :
$$M{n^{3 + }} = 3{d^4} = 4$$ unpaired electrons, $$C{r^{3 + }} = 3{d^3} = 3$$ unpaired electrons, $${V^{3 + }} = 3{d^2} = 2$$ unpaired electrons. $$C{r^{3 + }}$$ is most stable out of these in aqueous solution because it has half-filled $${t_{2g}}$$ level $$\left( {{\text{i}}{\text{.e}}{\text{.}},\,t_{2g}^3} \right).$$