The compound that gets oxidised even on exposure to atmosphere is:

Options

A. `Co_(2)(SO_(4))_(3)`
B. `NiSO_(4)`
C. `KMnO_(4)`
D. `FeSO_(4)`

Explanation

To solve the question regarding which compound gets oxidized even on exposure to the atmosphere, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Compounds**: The question provides four compounds:
- Cobalt sulfate (CoSO4)
- Nickel sulfate (NiSO4)
- Potassium permanganate (KMnO4)
- Ferrous sulfate (FeSO4)

2. **Analyze Each Compound**:
- **Cobalt sulfate (CoSO4)**: This compound is stable and does not readily oxidize in the presence of atmospheric oxygen.
- **Nickel sulfate (NiSO4)**: Similar to cobalt sulfate, nickel sulfate is also stable and does not oxidize easily in the atmosphere.
- **Potassium permanganate (KMnO4)**: This is a strong oxidizing agent, but it does not get oxidized itself; rather, it can oxidize other substances.
- **Ferrous sulfate (FeSO4)**: This compound is known to be susceptible to oxidation. When exposed to air, it reacts with oxygen and moisture present in the atmosphere.

3. **Chemical Reaction of Ferrous Sulfate**:
- When FeSO4 is exposed to the atmosphere, it can react with water vapor and oxygen. The reaction can be represented as follows:
\[ 4 \text{FeSO}_4 + \text{O}_2 + 6 \text{H}_2\text{O} \rightarrow 4 \text{Fe(OH)}_3 + 4 \text{H}_2\text{SO}_4 \]
- The product formed is basic ferrous sulfate, which indicates that FeSO4 gets oxidized.

4. **Conclusion**: Based on the analysis, the compound that gets oxidized even on exposure to the atmosphere is **Ferrous sulfate (FeSO4)**.

### Final Answer:
The compound that gets oxidized even on exposure to the atmosphere is **FeSO4 (Ferrous sulfate)**.