`MnO_(2)` is the most important oxide of manganese , `MnO_(2)` occurs natually as the black coloured mineral pyrolusite. It is an oxidising agent, and decomposes to `Mn_(3)O_(4)` on heating to `530^(@)`C. It is used in the preparation of potassium permanaganate and in the productioon of `Cl_(2)` gas. Over half million tonnes per year of `MnO_(2)` is used in dry batteries.
Q. In which of the following species, the colour is due to charge transfer?
(I)`[Mn(OH)_(4)]^(2-)` (II)`MnO_(4)^(2-)` (III)`MnO_(4)` (IV)`KMnO_(4)`

Options

A. I, II, III
B. II, IV
C. I, III
D. only IV

Answer

To determine which of the given species exhibit color due to charge transfer, we need to analyze the oxidation states of manganese in each compound and the electronic transitions involved.

### Step-by-Step Solution:

1. **Identify the oxidation states of manganese in each species:**
- **(I) \([Mn(OH)_{4}]^{2-}\)**:
- The hydroxide ion \((OH^{-})\) has a charge of -1. Therefore, for 4 hydroxide ions, the total charge is -4.
- Let the oxidation state of Mn be \(x\).
- The equation is: \(x - 4 = -2\) → \(x = +2\).

- **(II) \(MnO_{4}^{2-}\)**:
- Oxygen has an oxidation state of -2. For 4 oxygen atoms, the total charge is -8.
- Let the oxidation state of Mn be \(x\).
- The equation is: \(x - 8 = -2\) → \(x = +6\).

- **(III) \(MnO_{4}\)**:
- Again, with 4 oxygen atoms, the total charge is -8.
- Let the oxidation state of Mn be \(x\).
- The equation is: \(x - 8 = 0\) → \(x = +7\).

- **(IV) \(KMnO_{4}\)**:
- Potassium (K) has a charge of +1, and oxygen contributes -8 from 4 oxygen atoms.
- Let the oxidation state of Mn be \(x\).
- The equation is: \(x - 8 + 1 = 0\) → \(x = +7\).

2. **Analyze the color due to charge transfer:**
- **Charge Transfer (CT) Mechanism**: Color in transition metal complexes often arises from d-d transitions or charge transfer transitions. Charge transfer occurs when an electron moves from a ligand to the metal (Ligand to Metal Charge Transfer, LMCT) or from the metal to the ligand (Metal to Ligand Charge Transfer, MLCT).

- **(I) \([Mn(OH)_{4}]^{2-}\)**: Mn is in +2 oxidation state (3d^5 configuration). This species may have some color but is less likely to show strong color due to charge transfer.

- **(II) \(MnO_{4}^{2-}\)**: Mn is in +6 oxidation state (3d^4 configuration). This species can exhibit color due to charge transfer from oxygen to manganese.

- **(III) \(MnO_{4}\)**: Mn is in +7 oxidation state (3d^0 configuration). This species is colorless due to the absence of d-electrons for transitions.

- **(IV) \(KMnO_{4}\)**: Similar to \(MnO_{4}\), Mn is in +7 oxidation state. However, it shows a deep purple color due to LMCT from the oxygen ligands to the Mn.

3. **Conclusion**: The species that exhibit color due to charge transfer are:
- **(II) \(MnO_{4}^{2-}\)** and **(IV) \(KMnO_{4}\)**.

### Final Answer:
The species in which the color is due to charge transfer are \(MnO_{4}^{2-}\) and \(KMnO_{4}\).