Which of the following shows maximum number of oxidation states :-

Options

A. Cr
B. Fe
C. Mn
D. V

Answer

To determine which of the given elements shows the maximum number of oxidation states, we will analyze the valence electronic configurations of each element and calculate their possible oxidation states.

### Step-by-Step Solution:

1. **Identify the Elements and Their Electronic Configurations:**
- Chromium (Cr): [Ar] 3d⁵ 4s¹
- Iron (Fe): [Ar] 3d⁶ 4s²
- Manganese (Mn): [Ar] 3d⁵ 4s²
- Promethium (Pm): [Xe] 4f⁵ 6s²

2. **Calculate Oxidation States for Each Element:**
- **Chromium (Cr):**
- Can lose 1 electron from 4s: +1
- Can lose 2 electrons (1 from 4s and 1 from 3d): +2
- Can lose 3 electrons (2 from 4s and 1 from 3d): +3
- Can lose 4 electrons (3 from 3d): +4
- Can lose 5 electrons (4 from 3d): +5
- Can lose 6 electrons (5 from 3d): +6
- Total oxidation states: +1, +2, +3, +4, +5, +6 (6 oxidation states)

- **Iron (Fe):**
- Can lose 2 electrons from 4s: +2
- Can lose 3 electrons (2 from 4s and 1 from 3d): +3
- Can lose 4 electrons (3 from 3d): +4
- Can lose 5 electrons (4 from 3d): +5
- Can lose 6 electrons (5 from 3d): +6
- Total oxidation states: +2, +3, +4, +5, +6 (5 oxidation states)

- **Manganese (Mn):**
- Can lose 2 electrons from 4s: +2
- Can lose 3 electrons (2 from 4s and 1 from 3d): +3
- Can lose 4 electrons (3 from 3d): +4
- Can lose 5 electrons (4 from 3d): +5
- Can lose 6 electrons (5 from 3d): +6
- Can lose 7 electrons (6 from 3d): +7
- Total oxidation states: +2, +3, +4, +5, +6, +7 (7 oxidation states)

- **Promethium (Pm):**
- Typically exhibits oxidation states of +3 and +4.
- Total oxidation states: +3, +4 (2 oxidation states)

3. **Compare the Number of Oxidation States:**
- Chromium: 6 oxidation states
- Iron: 5 oxidation states
- Manganese: 7 oxidation states
- Promethium: 2 oxidation states

4. **Conclusion:**
- Manganese shows the maximum number of oxidation states, which is 7.

### Final Answer:
**Manganese (Mn) shows the maximum number of oxidation states.**