Cerium `(Z= 58)` is an important nember of the lanthanoids . Which of the following statements about cerium is incorrect ?

Options

A. The common oxidation states of cerium are +3 and +4.
B. The +3 oxidation state of cerium is more stable tan +4 oxidation state.
C. The +4 oxidation state of cerium is not known in solutions.
D. Cerium (IV)acts as an oxidising agent.

Explanation

To determine which statement about cerium (Z=58) is incorrect, we will analyze the properties and oxidation states of cerium.

### Step-by-Step Solution:

1. **Identify the Oxidation States of Cerium**:
- Cerium has two common oxidation states: +3 and +4. This is a fundamental property of cerium and is true.

2. **Stability of Oxidation States**:
- Among the two oxidation states, cerium in the +3 oxidation state is more stable than in the +4 oxidation state. This is due to the electronic configuration and the tendency of cerium to lose electrons. This statement is also correct.

3. **Presence of +4 Oxidation State in Solution**:
- The statement that the +4 oxidation state of cerium is not known in solution is incorrect. In fact, cerium in the +4 oxidation state can exist in various solutions and is known to act as an oxidizing agent. Therefore, this statement is false.

4. **Conclusion**:
- After analyzing the statements, the incorrect statement about cerium is that the +4 oxidation state is not known in solution.

### Final Answer:
The incorrect statement about cerium is: "The +4 oxidation state of cerium is not known in solution."

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