Which of the following would be diamagnetic ?

Options

A. `Cu^(2+)`
B. `Ni^(2+)`
C. `Cd^(2+)`
D. `Ti^(3+)`

Explanation

To determine which of the given ions is diamagnetic, we need to analyze the electronic configurations of each ion and check for unpaired electrons. Diamagnetic substances have all their electrons paired, while paramagnetic substances have one or more unpaired electrons.

### Step-by-Step Solution:

1. **Identify the Ions**: The ions we need to analyze are Cu²⁺, Ni²⁺, Cd²⁺, and Ti³⁺.

2. **Determine the Atomic Numbers**:
- Copper (Cu): Atomic number 29
- Nickel (Ni): Atomic number 28
- Cadmium (Cd): Atomic number 48
- Titanium (Ti): Atomic number 22

3. **Write the Electronic Configurations**:
- **Cu (Copper)**:
- Ground state: [Ar] 3d¹⁰ 4s¹
- For Cu²⁺: Remove one electron from 4s and one from 3d.
- Configuration: [Ar] 3d⁹ 4s⁰
- **Ni (Nickel)**:
- Ground state: [Ar] 3d⁸ 4s²
- For Ni²⁺: Remove two electrons from 4s.
- Configuration: [Ar] 3d⁸ 4s⁰
- **Cd (Cadmium)**:
- Ground state: [Kr] 4d¹⁰ 5s²
- For Cd²⁺: Remove two electrons from 5s.
- Configuration: [Kr] 4d¹⁰ 5s⁰
- **Ti (Titanium)**:
- Ground state: [Ar] 3d² 4s²
- For Ti³⁺: Remove two electrons from 4s and one from 3d.
- Configuration: [Ar] 3d¹ 4s⁰

4. **Count Unpaired Electrons**:
- **Cu²⁺**: [Ar] 3d⁹ 4s⁰ has 1 unpaired electron (paramagnetic).
- **Ni²⁺**: [Ar] 3d⁸ 4s⁰ has 2 unpaired electrons (paramagnetic).
- **Cd²⁺**: [Kr] 4d¹⁰ 5s⁰ has 0 unpaired electrons (diamagnetic).
- **Ti³⁺**: [Ar] 3d¹ 4s⁰ has 1 unpaired electron (paramagnetic).

5. **Conclusion**: The only ion that is diamagnetic (having all electrons paired) is **Cd²⁺**.

### Final Answer:
The ion that is diamagnetic is **Cd²⁺**.

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