Which of the following is a diamagnetic ion: (Atomic numbers of Sc, V, Mn and Cu are 21, 23, 25 and 29 respectively)

Options

A. `V^(2+)`
B. `Sc^(3+)`
C. `Cu^(2+)`
D. `Mn^(3+)`

Answer

To determine which of the given ions is diamagnetic, we need to analyze the electron configurations of each ion and check for unpaired electrons. A diamagnetic ion has all its electrons paired, while a paramagnetic ion has one or more unpaired electrons.

### Step-by-Step Solution:

1. **Identify the ions**: The ions we need to analyze are V²⁺, Sc³⁺, Cu²⁺, and Mn³⁺.

2. **Determine the electron configurations**:
- **Vanadium (V)**: Atomic number 23
- Neutral V: [Ar] 4s² 3d³
- For V²⁺: Remove 2 electrons (from 4s): [Ar] 3d³
- **Scandium (Sc)**: Atomic number 21
- Neutral Sc: [Ar] 4s² 3d¹
- For Sc³⁺: Remove 3 electrons (2 from 4s and 1 from 3d): [Ar]
- **Copper (Cu)**: Atomic number 29
- Neutral Cu: [Ar] 4s¹ 3d¹⁰
- For Cu²⁺: Remove 2 electrons (1 from 4s and 1 from 3d): [Ar] 3d⁹
- **Manganese (Mn)**: Atomic number 25
- Neutral Mn: [Ar] 4s² 3d⁵
- For Mn³⁺: Remove 3 electrons (2 from 4s and 1 from 3d): [Ar] 3d⁴

3. **Analyze the electron configurations for unpaired electrons**:
- **V²⁺**: [Ar] 3d³ has 3 unpaired electrons (paramagnetic).
- **Sc³⁺**: [Ar] has no unpaired electrons (diamagnetic).
- **Cu²⁺**: [Ar] 3d⁹ has 1 unpaired electron (paramagnetic).
- **Mn³⁺**: [Ar] 3d⁴ has 4 unpaired electrons (paramagnetic).

4. **Conclusion**: The only ion that is diamagnetic (having all paired electrons) is Sc³⁺.

### Final Answer:
The diamagnetic ion among the given options is **Sc³⁺**.