Which one of the transittion metal ions is coloured in aqueous solution?

Options

A. `Cu^(+)`
B. `Zn^(2+)`
C. `Sc^(3+)`
D. `V^(4+)`

Explanation

To determine which transition metal ion is colored in aqueous solution, we need to analyze the electronic configurations of the given ions and identify if they have unpaired electrons. The presence of unpaired electrons is crucial for the occurrence of d-d transitions, which are responsible for the color in transition metal complexes.

### Step-by-Step Solution:

1. **Identify the Ions**: The ions given are Cu⁺, Zn²⁺, Sc³⁺, and V⁴⁺.

2. **Write the Electronic Configuration**:
- **Cu⁺ (Cuprous ion)**:
- Atomic number of Cu = 29
- Electronic configuration of Cu = [Ar] 3d¹⁰ 4s²
- For Cu⁺, we remove one electron:
- Cu⁺: [Ar] 3d¹⁰ 4s⁰
- No unpaired electrons (3d¹⁰).

- **Zn²⁺ (Zinc ion)**:
- Atomic number of Zn = 30
- Electronic configuration of Zn = [Ar] 3d¹⁰ 4s²
- For Zn²⁺, we remove two electrons:
- Zn²⁺: [Ar] 3d¹⁰ 4s⁰
- No unpaired electrons (3d¹⁰).

- **Sc³⁺ (Scandium ion)**:
- Atomic number of Sc = 21
- Electronic configuration of Sc = [Ar] 3d¹ 4s²
- For Sc³⁺, we remove three electrons:
- Sc³⁺: [Ar] 3d⁰ 4s⁰
- No unpaired electrons (3d⁰).

- **V⁴⁺ (Vanadium ion)**:
- Atomic number of V = 23
- Electronic configuration of V = [Ar] 3d³ 4s²
- For V⁴⁺, we remove four electrons:
- V⁴⁺: [Ar] 3d¹ 4s⁰
- One unpaired electron (3d¹).

3. **Determine Color**:
- Ions with no unpaired electrons (Cu⁺, Zn²⁺, Sc³⁺) will not show color because they cannot undergo d-d transitions.
- V⁴⁺ has one unpaired electron, which allows for d-d transitions when it interacts with ligands in solution. This transition absorbs certain wavelengths of light, resulting in the appearance of color.

4. **Conclusion**:
- The only transition metal ion that is colored in aqueous solution is **V⁴⁺ (Vanadium ion)**.

### Final Answer:
**V⁴⁺ (Vanadium ion) is colored in aqueous solution.**