Which of the following ion has three unpaired d-electrons

Options

A. `Ti^(2+)`
B. `V^(3+)`
C. `Cr^(3+)`
D. `Mn^(2+)`

Answer

To determine which ion has three unpaired d-electrons, we will analyze the electronic configurations of the given ions step by step.

### Step 1: Identify the Electronic Configuration of Each Element
1. **Titanium (Ti)**: Atomic number = 22
- Electronic configuration: \( \text{Ti} = [\text{Ar}] 3d^2 4s^2 \)

2. **Vanadium (V)**: Atomic number = 23
- Electronic configuration: \( \text{V} = [\text{Ar}] 3d^3 4s^2 \)

3. **Chromium (Cr)**: Atomic number = 24
- Electronic configuration: \( \text{Cr} = [\text{Ar}] 3d^5 4s^1 \)

4. **Manganese (Mn)**: Atomic number = 25
- Electronic configuration: \( \text{Mn} = [\text{Ar}] 3d^5 4s^2 \)

### Step 2: Determine the Electronic Configuration of the Ions
1. **Titanium ion (Ti²⁺)**:
- Remove 2 electrons (from 4s and then from 3d)
- Configuration: \( \text{Ti}^{2+} = [\text{Ar}] 3d^2 \)

2. **Vanadium ion (V³⁺)**:
- Remove 3 electrons (2 from 4s and 1 from 3d)
- Configuration: \( \text{V}^{3+} = [\text{Ar}] 3d^2 \)

3. **Chromium ion (Cr³⁺)**:
- Remove 3 electrons (1 from 4s and 2 from 3d)
- Configuration: \( \text{Cr}^{3+} = [\text{Ar}] 3d^3 \)

4. **Manganese ion (Mn²⁺)**:
- Remove 2 electrons (2 from 4s)
- Configuration: \( \text{Mn}^{2+} = [\text{Ar}] 3d^5 \)

### Step 3: Count the Unpaired d-Electrons
1. **Ti²⁺ (3d²)**:
- Configuration: \( 3d^2 \) → 2 unpaired electrons

2. **V³⁺ (3d²)**:
- Configuration: \( 3d^2 \) → 2 unpaired electrons

3. **Cr³⁺ (3d³)**:
- Configuration: \( 3d^3 \) → 3 unpaired electrons

4. **Mn²⁺ (3d^5)**:
- Configuration: \( 3d^5 \) → 5 unpaired electrons

### Conclusion
The ion with three unpaired d-electrons is **Chromium (Cr³⁺)**.