Which one of the following transition metal ions is diamagnetic?

Options

A. `Co^(2+)`
B. `Ni^(2+)`
C. `Cu^(2+)`
D. `Zn^(2+)`

Explanation

To determine which transition metal ion is diamagnetic, we need to analyze the electron configurations of the given ions and check for the presence of unpaired electrons. Here’s the step-by-step solution:

### Step 1: Understand Diamagnetism and Paramagnetism
- **Diamagnetic** species have no unpaired electrons.
- **Paramagnetic** species have one or more unpaired electrons.

### Step 2: Analyze Each Ion
We will analyze the electron configuration of each transition metal ion provided in the options.

#### Option 1: Cobalt (Co²⁺)
- Atomic number of Co = 27
- Ground state configuration: [Ar] 3d⁷ 4s²
- For Co²⁺, we remove 2 electrons (from 4s and 3d):
- Configuration: 3d⁷
- Filling the 3d orbitals:
- 3d: ↑↓ ↑↓ ↑↓ ↑ ↑ (3 unpaired electrons)
- **Conclusion**: Co²⁺ is paramagnetic.

#### Option 2: Nickel (Ni²⁺)
- Atomic number of Ni = 28
- Ground state configuration: [Ar] 3d⁸ 4s²
- For Ni²⁺, we remove 2 electrons:
- Configuration: 3d⁸
- Filling the 3d orbitals:
- 3d: ↑↓ ↑↓ ↑↓ ↑ ↑ (2 unpaired electrons)
- **Conclusion**: Ni²⁺ is paramagnetic.

#### Option 3: Copper (Cu²⁺)
- Atomic number of Cu = 29
- Ground state configuration: [Ar] 3d¹⁰ 4s¹
- For Cu²⁺, we remove 2 electrons:
- Configuration: 3d⁹
- Filling the 3d orbitals:
- 3d: ↑↓ ↑↓ ↑↓ ↑ ↑ (1 unpaired electron)
- **Conclusion**: Cu²⁺ is paramagnetic.

#### Option 4: Zinc (Zn²⁺)
- Atomic number of Zn = 30
- Ground state configuration: [Ar] 3d¹⁰ 4s²
- For Zn²⁺, we remove 2 electrons:
- Configuration: 3d¹⁰
- Filling the 3d orbitals:
- 3d: ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ (0 unpaired electrons)
- **Conclusion**: Zn²⁺ is diamagnetic.

### Final Answer
The transition metal ion that is diamagnetic is **Zn²⁺**.

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