Q24 / 180 · COMEDK 2023 (Morning Shift) · Chemistry
$\mathrm{Ti}^{2+}$ is purple while $\mathrm{Ti}^{4+}$ is colourless because
- AThere is no crystal field effect in $\mathrm{Ti}^{4+}$
- B$\mathrm{Ti}^{4+}$ has $3 d^2$ configuration
- Correct answerC$\mathrm{Ti}^{2+}$ has $3 d^2$ configuration
- D$\mathrm{Ti}^{2+}$ is very small cation when compared to $\mathrm{Ti}^{2+}$ and hence, doesn't absorb any radiation
Solution
The electronic configuration of titanium is $[Ar] 3d^2 4s^2$.
For $\mathrm{Ti}^{2+}$, the configuration is $[Ar] 3d^2$. Since there are two electrons in the $d$-orbitals, $d-d$ transitions are possible when light is absorbed, resulting in the purple color.
For $\mathrm{Ti}^{4+}$, the configuration is $[Ar] 3d^0$. Since there are no electrons in the $d$-orbitals, $d-d$ transitions cannot occur, making the ion colourless.
Option (3) correctly identifies the electronic configuration of $\mathrm{Ti}^{2+}$ as $3d^2$, which is the reason for its color due to $d-d$ transitions.
Answer: $\mathrm{Ti}^{2+}$ has $3 d^2$ configuration
For $\mathrm{Ti}^{2+}$, the configuration is $[Ar] 3d^2$. Since there are two electrons in the $d$-orbitals, $d-d$ transitions are possible when light is absorbed, resulting in the purple color.
For $\mathrm{Ti}^{4+}$, the configuration is $[Ar] 3d^0$. Since there are no electrons in the $d$-orbitals, $d-d$ transitions cannot occur, making the ion colourless.
Option (3) correctly identifies the electronic configuration of $\mathrm{Ti}^{2+}$ as $3d^2$, which is the reason for its color due to $d-d$ transitions.
Answer: $\mathrm{Ti}^{2+}$ has $3 d^2$ configuration
Hence, the correct answer is option: 'C'.