Which of the following ion is diamagnetic?

Options

A. `Fe^(2+)`
B. `Cr^(3+)`
C. `Zn^(2+)`
D. `Cu^(2+)`

Explanation

To determine which of the following ions is diamagnetic, we need to analyze the electronic configurations of each ion and check for unpaired electrons. A diamagnetic substance has all its electrons paired, while a paramagnetic substance has unpaired electrons.

Let's evaluate the given ions step by step:

### Step 1: Determine the electronic configuration of each ion.

1. **Fe²⁺ (Iron ion)**
- Atomic number of Fe = 26
- Ground state configuration of Fe = [Ar] 4s² 3d⁶
- For Fe²⁺, we remove 2 electrons (from 4s):
- Configuration of Fe²⁺ = 3d⁶
- Distribution of 3d electrons:
- 1, 2, 3, 4, 5, 6 (4 unpaired electrons)

2. **Cr³⁺ (Chromium ion)**
- Atomic number of Cr = 24
- Ground state configuration of Cr = [Ar] 4s¹ 3d⁵ (due to exceptional configuration)
- For Cr³⁺, we remove 3 electrons (1 from 4s and 2 from 3d):
- Configuration of Cr³⁺ = 3d³
- Distribution of 3d electrons:
- 1, 2, 3 (3 unpaired electrons)

3. **Zn²⁺ (Zinc ion)**
- Atomic number of Zn = 30
- Ground state configuration of Zn = [Ar] 4s² 3d¹⁰
- For Zn²⁺, we remove 2 electrons (from 4s):
- Configuration of Zn²⁺ = 3d¹⁰
- Distribution of 3d electrons:
- 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 (all paired)

4. **Cu²⁺ (Copper ion)**
- Atomic number of Cu = 29
- Ground state configuration of Cu = [Ar] 4s¹ 3d¹⁰ (due to exceptional configuration)
- For Cu²⁺, we remove 2 electrons (1 from 4s and 1 from 3d):
- Configuration of Cu²⁺ = 3d⁹
- Distribution of 3d electrons:
- 1, 2, 3, 4, 5, 6, 7, 8, 9 (1 unpaired electron)

### Step 2: Identify the ion that is diamagnetic.

- **Fe²⁺**: 4 unpaired electrons (paramagnetic)
- **Cr³⁺**: 3 unpaired electrons (paramagnetic)
- **Zn²⁺**: 0 unpaired electrons (diamagnetic)
- **Cu²⁺**: 1 unpaired electron (paramagnetic)

### Conclusion:
The ion that is diamagnetic is **Zn²⁺**.