Highest tendency for `M^(+3) rarrM^(+2)` is in

Options

A. `Mn`
B. `Cr`
C. `Fe`
D. All have same

Answer

To determine which metal has the highest tendency to convert from the +3 oxidation state (M³⁺) to the +2 oxidation state (M²⁺), we will analyze the electronic configurations of manganese (Mn), chromium (Cr), and iron (Fe) in both oxidation states.

### Step-by-Step Solution:

1. **Identify the Metals and Their Atomic Numbers:**
- Manganese (Mn) - Atomic number 25
- Chromium (Cr) - Atomic number 24
- Iron (Fe) - Atomic number 26

2. **Write the Ground State Electronic Configurations:**
- Mn: [Ar] 3d⁵ 4s²
- Cr: [Ar] 3d⁵ 4s¹
- Fe: [Ar] 3d⁶ 4s²

3. **Determine the Electronic Configurations for M³⁺:**
- For M³⁺, three electrons are removed (first from 4s, then from 3d):
- Mn³⁺: [Ar] 3d⁴ (removing 2 from 4s and 1 from 3d)
- Cr³⁺: [Ar] 3d³ (removing 1 from 4s and 2 from 3d)
- Fe³⁺: [Ar] 3d⁵ (removing 2 from 4s and 1 from 3d)

4. **Determine the Electronic Configurations for M²⁺:**
- For M²⁺, two electrons are removed:
- Mn²⁺: [Ar] 3d⁵ (removing 2 from 4s)
- Cr²⁺: [Ar] 3d⁴ (removing 2 from 4s)
- Fe²⁺: [Ar] 3d⁶ (removing 2 from 4s)

5. **Analyze Stability of Electronic Configurations:**
- A half-filled (3d⁵) or fully filled (3d¹⁰) configuration is more stable than an incompletely filled one.
- For Mn: Transition from 3d⁴ (M³⁺) to 3d⁵ (M²⁺) increases stability (increases to half-filled).
- For Cr: Transition from 3d³ (M³⁺) to 3d⁴ (M²⁺) is less stable (increases but not to half-filled).
- For Fe: Transition from 3d⁵ (M³⁺) to 3d⁶ (M²⁺) decreases stability (from half-filled to incompletely filled).

6. **Conclusion:**
- Manganese (Mn) has the highest tendency to convert from M³⁺ to M²⁺ because this transition leads to a more stable half-filled configuration.

### Final Answer:
The metal with the highest tendency for M³⁺ to M²⁺ conversion is **Mn (Manganese)**.