The incorrect statement(s) about `Cr^(2+) and Mn^(3+)` is (are)
[Atomic numbers of Cr = 24 and Mn = 25]

Options

A. `Cr^(2+)` is a reducing agent
B. `Mn^(3+)` is an oxidizing agent
C. Both `Cr^(2+) and Mn^(3+)` exhibit `d^(4)` electronic configuration
D. When `Cr^(2+)` is used as a reducing agent, the chromium ion attains `d^(5)` electronic configuration

Answer

To determine the incorrect statement(s) about Cr²⁺ and Mn³⁺, we will analyze each statement based on the properties and electronic configurations of these ions.

### Step 1: Analyze the first statement
**Statement:** Cr²⁺ is a reducing agent.

- **Explanation:** Cr²⁺ can lose electrons to form higher oxidation states, such as Cr³⁺ and Cr⁶⁺. Since it can donate electrons, it acts as a reducing agent.
- **Conclusion:** This statement is **correct**.

### Step 2: Analyze the second statement
**Statement:** Mn³⁺ is an oxidizing agent.

- **Explanation:** Mn³⁺ can gain electrons to form Mn²⁺. Gaining electrons indicates that it can oxidize other substances, thus acting as an oxidizing agent.
- **Conclusion:** This statement is **correct**.

### Step 3: Analyze the third statement
**Statement:** Both Cr²⁺ and Mn³⁺ exhibit d⁴ electronic configuration.

- **Explanation:**
- Cr²⁺ has an electronic configuration of [Ar] 3d⁴ (it loses two electrons from the 4s and 3d orbitals).
- Mn³⁺ has an electronic configuration of [Ar] 3d⁴ (it loses three electrons, two from 4s and one from 3d).
- **Conclusion:** This statement is **correct**.

### Step 4: Analyze the fourth statement
**Statement:** When Cr²⁺ is used as a reducing agent, the chromium ion attains d⁵ electronic configuration.

- **Explanation:** When Cr²⁺ acts as a reducing agent, it can be oxidized to Cr³⁺, which has a d³ configuration. However, the statement claims that it attains a d⁵ configuration, which is incorrect.
- **Conclusion:** This statement is **incorrect**.

### Final Conclusion
The incorrect statement about Cr²⁺ and Mn³⁺ is the fourth one: "When Cr²⁺ is used as a reducing agent, the chromium ion attains d⁵ electronic configuration."

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