Determine Correctness of Statements on Coloured and Diamagnetic Complex Ions

To determine the correctness of Statement I, we analyze the electronic configurations of the transition metal ions:
$\text{Ti}^{4+} ([ \text{Ar} ] 3d^0)$ is colorless due to the absence of $d$-electrons, whereas $\text{V}^{2+} ([ \text{Ar} ] 3d^3)$, $\text{Mn}^{2+} ([ \text{Ar} ] 3d^5)$, $\text{Fe}^{3+} ([ \text{Ar} ] 3d^5)$, and $\text{Cr}^{2+} ([ \text{Ar} ] 3d^4)$ all contain partially filled $d$-orbitals and are coloured.
Out of the four given pairs, both ions are coloured in the following three pairs: $[\text{V}^{2+}, \text{Mn}^{2+}]$, $[\text{Mn}^{2+}, \text{Fe}^{3+}]$, and $[\text{V}^{2+}, \text{Cr}^{2+}]$. Therefore, Statement I is correct.

To determine the correctness of Statement II, we analyze the electronic configurations of the lanthanide and actinide ions:
$\text{La}^{3+} (4f^0)$, $\text{Yb}^{2+} (4f^{14})$, $\text{Lu}^{3+} (4f^{14})$, $\text{Ce}^{4+} (4f^0)$, $\text{Ac}^{3+} (5f^0)$, and $\text{Lr}^{3+} (5f^{14})$ all have completely empty ($f^0$) or fully filled ($f^{14}$) $f$-subshells. Having zero unpaired electrons, all of these ions are diamagnetic.

Thus, both ions are diamagnetic in all 3 given pairs: $[\text{La}^{3+}, \text{Yb}^{2+}]$, $[\text{Lu}^{3+}, \text{Ce}^{4+}]$, and $[\text{Ac}^{3+}, \text{Lr}^{3+}]$. Therefore, Statement II is correct.

Hence, both Statement I and Statement II are correct.

Correct Option: A