Which of the following ions give coloured aqueous solution?

Options

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

Explanation

To determine which of the given ions give colored aqueous solutions, we need to analyze the electronic configurations of the ions and check for the presence of unpaired electrons in their d-orbitals. The presence of unpaired electrons is essential for the absorption of visible light, leading to color in the solution.

### Step-by-Step Solution:

1. **Understanding the Concept of Color in Transition Metal Ions**:
- Transition metal ions often exhibit color due to the presence of unpaired electrons in their d-orbitals. When these ions are in solution, they can interact with ligands (like water), causing the d-orbitals to split into different energy levels. Electrons can be excited from a lower energy level to a higher one, and the energy absorbed corresponds to specific wavelengths of visible light, which we perceive as color.

2. **Analyzing Each Ion**:
- We will analyze the electronic configuration of each ion provided in the options.

3. **Nickel (Ni²⁺)**:
- Atomic number: 28
- Electronic configuration: [Ar] 3d⁸ 4s²
- For Ni²⁺: [Ar] 3d⁸ 4s⁰
- Number of unpaired electrons: 2 (in the 3d subshell)
- Conclusion: Ni²⁺ gives a green color in aqueous solution.

4. **Iron (Fe²⁺)**:
- Atomic number: 26
- Electronic configuration: [Ar] 3d⁶ 4s²
- For Fe²⁺: [Ar] 3d⁶ 4s⁰
- Number of unpaired electrons: 4 (in the 3d subshell)
- Conclusion: Fe²⁺ gives a light green color in aqueous solution.

5. **Copper (Cu²⁺)**:
- Atomic number: 29
- Electronic configuration: [Ar] 3d¹⁰ 4s¹
- For Cu²⁺: [Ar] 3d⁹ 4s⁰
- Number of unpaired electrons: 1 (in the 3d subshell)
- Conclusion: Cu²⁺ gives a blue color in aqueous solution.

6. **Copper (Cu⁺)**:
- For Cu⁺: [Ar] 3d¹⁰ 4s⁰
- Number of unpaired electrons: 0 (all electrons are paired)
- Conclusion: Cu⁺ does not give any color in aqueous solution.

7. **Final Conclusion**:
- The ions that give colored aqueous solutions are Ni²⁺, Fe²⁺, and Cu²⁺.
- The ion Cu⁺ does not give any color due to the absence of unpaired electrons.

### Summary of Results:
- **Colored Ions**: Ni²⁺ (green), Fe²⁺ (light green), Cu²⁺ (blue)
- **Non-Colored Ion**: Cu⁺ (no color)