Incorrect statement with reference to Ce (Z = 58).

Options

A. `Ce^(4+)` is a reducing agent.
B. Ce in +3 oxidation state is more stable than in +4.
C. Atomic size of Ce is more than that of Lu.
D. Ce shows common oxidation states of +3 and +4.

Explanation

To determine the incorrect statement regarding Cerium (Ce, Z = 58), we will analyze the provided options step by step.

### Step 1: Understand the Electronic Configuration of Cerium
- The atomic number of Cerium (Ce) is 58. Its electronic configuration can be written as:
\[ \text{Ce: } [Xe] 4f^1 5d^1 6s^2 \]
- This configuration indicates that Cerium has electrons in the 4f, 5d, and 6s subshells.

### Step 2: Analyze the Electronic Configuration of Ce^4+
- When Cerium loses four electrons to form Ce^4+, the electronic configuration changes as follows:
- Two electrons are removed from the 6s subshell.
- One electron is removed from the 5d subshell.
- One electron is removed from the 4f subshell.

Thus, the electronic configuration of Ce^4+ is:
\[ \text{Ce}^{4+}: [Xe] 4f^0 5d^0 6s^0 \]
- This indicates that Ce^4+ has achieved a noble gas configuration.

### Step 3: Determine the Nature of Ce^4+
- A reducing agent is a species that can be oxidized further, meaning it can lose more electrons.
- Since Ce^4+ has reached a noble gas configuration, it cannot lose any more electrons to form Ce^5+. Therefore, it cannot act as a reducing agent.
- Thus, the statement "Ce^4+ is a reducing agent" is incorrect.

### Step 4: Evaluate Other Options
- **Option B:** "Ce^3+ oxidation state is more stable than Ce^4+."
- This is correct because the energy required to remove three electrons (to form Ce^3+) is less than that required to remove four electrons (to form Ce^4+).

- **Option C:** "Atomic size of Ce is more than that of Lu."
- This is also correct due to lanthanide contraction, where the atomic size decreases as the atomic number increases in the lanthanide series.

- **Option D:** "Ce shows common oxidation states of +3 and +4."
- This is correct as well; Ce commonly exhibits +3 and +4 oxidation states.

### Conclusion
After analyzing all options, the incorrect statement is:
- **A:** "Ce^4+ is a reducing agent."

### Final Answer
The incorrect statement with reference to Ce (Z = 58) is:
- **A:** "Ce^4+ is a reducing agent."

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