The ion that cannot undergo disproportionation is :

Options

A. `ClO_4 ^ (-)`
B. `ClO_3^(-)`
C. `ClO_2^(-)`
D. `ClO^(-)`

Answer

To solve the question regarding which ion cannot undergo disproportionation, we will follow these steps:

### Step 1: Understand Disproportionation
Disproportionation is a specific type of redox reaction where a single substance is simultaneously oxidized and reduced, resulting in two different products.

### Step 2: Identify the Ions
The ions given in the question are:
- ClO4^-
- ClO3^-
- ClO2^-
- ClO^-

### Step 3: Determine the Oxidation States
We will calculate the oxidation state of chlorine in each ion.

1. **For ClO4^-**:
- Let the oxidation state of Cl be \( x \).
- The equation becomes: \( x + 4(-2) = -1 \)
- Simplifying: \( x - 8 = -1 \) → \( x = +7 \)

2. **For ClO3^-**:
- Let the oxidation state of Cl be \( x \).
- The equation becomes: \( x + 3(-2) = -1 \)
- Simplifying: \( x - 6 = -1 \) → \( x = +5 \)

3. **For ClO2^-**:
- Let the oxidation state of Cl be \( x \).
- The equation becomes: \( x + 2(-2) = -1 \)
- Simplifying: \( x - 4 = -1 \) → \( x = +3 \)

4. **For ClO^-**:
- Let the oxidation state of Cl be \( x \).
- The equation becomes: \( x + (-2) = -1 \)
- Simplifying: \( x - 2 = -1 \) → \( x = +1 \)

### Step 4: Analyze the Oxidation States
Now, we analyze whether each ion can undergo disproportionation based on its oxidation states:

- **ClO4^-**: Chlorine is in its highest oxidation state (+7). It cannot be oxidized further, so it cannot undergo disproportionation.
- **ClO3^-**: Chlorine can be reduced (to +5) and oxidized (to +7), so it can undergo disproportionation.
- **ClO2^-**: Chlorine can be reduced (to +3) and oxidized (to +5), so it can undergo disproportionation.
- **ClO^-**: Chlorine can be reduced (to -1) and oxidized (to +1), so it can undergo disproportionation.

### Conclusion
The ion that cannot undergo disproportionation is **ClO4^-**.

### Final Answer
**ClO4^-**