When the oxidation number of an element is maximum it can act only as………………

Answer

To solve the question "When the oxidation number of an element is maximum, it can act only as…", we need to understand the concept of oxidation numbers and their implications in redox reactions.

### Step-by-Step Solution:

1. **Understanding Oxidation Number**:
- The oxidation number (or oxidation state) of an element in a compound indicates the degree of oxidation of that element. It is a hypothetical charge that an atom would have if all bonds to atoms of different elements were completely ionic.

2. **Maximum Oxidation State**:
- When we say that an element has a maximum oxidation number, it means that it has lost the maximum number of electrons possible in that particular oxidation state. For example, in compounds like \( \text{MnO}_4^{-} \), manganese has an oxidation state of +7, which is its maximum for that element.

3. **Behavior of Elements with Maximum Oxidation States**:
- When an element reaches its maximum oxidation state, it is at a point where it cannot lose any more electrons. Therefore, it cannot act as a reducing agent (which donates electrons).

4. **Acting as an Oxidizing Agent**:
- Instead, elements in their maximum oxidation state can only act as oxidizing agents. An oxidizing agent is a substance that gains electrons in a chemical reaction and is reduced in the process. Since the element is already at its highest oxidation state, it can facilitate the oxidation of other substances by accepting electrons.

5. **Conclusion**:
- Therefore, when the oxidation number of an element is maximum, it can act only as an oxidizing agent.

### Final Answer:
When the oxidation number of an element is maximum, it can act only as an **oxidizing agent**.

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