The color of `KMnO_(4)` is due to

Options

A. d - d transition
B. `L to M` charge transfer transition
C. `sigma - sigma **` transition
D. `M to L` charge transfer transition

Answer

To determine the reason behind the color of potassium permanganate (KMnO₄), we can follow these steps:

### Step 1: Identify the central metal ion and its oxidation state
- In KMnO₄, the central metal ion is manganese (Mn).
- Manganese in KMnO₄ is in the +7 oxidation state.

### Step 2: Determine the electronic configuration of manganese in this state
- The atomic number of manganese (Mn) is 25.
- In the +7 oxidation state, manganese loses 7 electrons, resulting in the electronic configuration of Ar 3d⁰ 4s⁰. This means that there are no electrons in the 3d or 4s orbitals.

### Step 3: Understand the role of unpaired electrons in color
- The color of a compound is often due to the presence of unpaired electrons, which can undergo electronic transitions.
- However, in the case of KMnO₄, there are no unpaired electrons since the 3d and 4s orbitals are completely empty.

### Step 4: Consider charge transfer transitions
- Since KMnO₄ does not have unpaired electrons, we need to consider other mechanisms that could cause color.
- Charge transfer transitions can also lead to color in transition metal complexes. These can be classified into two types: ligand-to-metal charge transfer (LMCT) and metal-to-ligand charge transfer (MLCT).

### Step 5: Identify the type of charge transfer transition in KMnO₄
- In KMnO₄, the color arises primarily from ligand-to-metal charge transfer (LMCT). This occurs when an electron is excited from a molecular orbital of the ligand to a non-bonding or anti-bonding molecular orbital of the metal.
- This type of transition is responsible for the characteristic dark purple color of KMnO₄.

### Conclusion
- The color of KMnO₄ is due to ligand-to-metal charge transfer transitions.

### Final Answer
The color of KMnO₄ is due to **ligand-to-metal charge transfer transitions**.

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