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

Options

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

Answer

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

### Step 1: Identify the composition of KMnO4
Potassium permanganate is composed of potassium (K), manganese (Mn), and oxygen (O). The relevant ion in this compound is the permanganate ion, MnO4^-.

**Hint:** Look for the ions that make up the compound and focus on the transition metal involved.

### Step 2: Determine the oxidation state of manganese in KMnO4
In KMnO4, the oxidation state of manganese (Mn) can be calculated. The overall charge of the permanganate ion (MnO4^-) is -1. Since there are four oxygen atoms, each with a charge of -2, we can set up the equation:

Let the oxidation state of Mn be \( x \):
\[ x + 4(-2) = -1 \]
\[ x - 8 = -1 \]
\[ x = +7 \]

**Hint:** Use the charge balance method to find the oxidation state of the transition metal.

### Step 3: Analyze the electronic configuration of manganese
Manganese has an atomic number of 25, and its electronic configuration is:
\[ \text{Mn: } [Ar] 3d^5 4s^2 \]
In the +7 oxidation state (MnO4^-), manganese loses all its 3d and 4s electrons, resulting in a configuration of:
\[ 3d^0 4s^0 \]

**Hint:** Remember that the electronic configuration changes with oxidation states.

### Step 4: Consider the types of electronic transitions
In transition metal complexes, color is often due to d-d transitions (electrons moving between d-orbitals). However, in the case of Mn in the +7 oxidation state, there are no d-electrons (3d^0 configuration), which means d-d transitions cannot occur.

**Hint:** Reflect on how the absence of d-electrons affects the color of the compound.

### Step 5: Identify the type of charge transfer that occurs
Since there are no d-d transitions, we look for other types of electronic transitions. In KMnO4, we have ligand-to-metal charge transfer (LMCT). The oxygen atoms act as ligands and can donate electrons to the manganese ion. This transfer of charge from the ligand to the metal is responsible for the color of KMnO4.

**Hint:** Consider how ligands interact with the metal and the resulting electronic transitions.

### 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.