Question

The correct statement(s) about $C{r}^{2+}\text{and}M{n}^{3+}$ is/are:

• A. $C{r}^{2+}$ is a reducing agent
• B. $M{n}^{3+}$ is an oxidising agent
• C. Both $C{r}^{2+}\text{and}M{n}^{3+}$ exhibit $d^4$ electronic configuration
• D. When $C{r}^{2+}$ is used as a reducing agent the chromium ion attains a $d^5$ electronic configuration

Answer 1

Answer: (A), (B), (C)

Both $C{r}^{2+}\text{and}M{n}^{3+}$ exhibit $d^4$ electronic configuration

$C{r}^{2+}$ is strong reducing agent, because after losing one electron it becomes $C{r}^{3+}$, which has configuration $t_{\text{2g}}^3{e}_{\text{g}}^0$, hence more stable.
$C{r}^{2+}⟶C{r}^{3+}+e^{-}\text{(Oxidation)}$
(R.A.)
$M{n}^{3+}$ is a good oxidising agent because after gaining one electron it becomes $M{n}^{2+}$ which has $t_{\text{2g}}^3{e}_{\text{g}}^2$, electronic configuration, hence more stable.
$M{n}^{3+}+e^{-}⟶M{n}^{2+}\text{(Reduction)}$
(O.A.)
$\text{The electronic configuration of}Cr\text{is:}\left[Ar\right]3d^{5}4s^1$
After the removal of $2$ electrons from chromium, the electronic configuration of $C{r}^{2+}:\left[Ar\right]3d^{4}4s^0$
$\text{The electronic configuration of}Mn\text{is:}\left[Ar\right]3d^{5}4s^2$
After removing $3$ electrons from manganese, the electronic configuration of $M{n}^{3+}:\left[Ar\right]3d^{4}4s^0$