In which of the following pairs are both the ions coloured in aqueous solution-

Options

A. ` Ni^(2+), Ti^(3+) `
B. `Sc^(3+),Ti^(3+)`
C. `Sc^(3+), Co^(2+)`
D. `Ni^(2+), Cu^(+)`

Answer

To determine which pairs of ions are colored in aqueous solution, we need to analyze the electronic configurations of the ions and check for the presence of unpaired d-electrons. The presence of unpaired d-electrons is what typically gives rise to color in transition metal ions.

### Step-by-Step Solution:

1. **Identify the Ions**: We need to look at the pairs of ions provided in the question. For this example, let's consider the following ions:
- Nickel (Ni²⁺)
- Titanium (Ti³⁺)
- Scandium (Sc³⁺)
- Copper (Cu⁺)

2. **Determine the Atomic Numbers and Electron Configurations**:
- **Nickel (Ni)**: Atomic number = 28
- Electron configuration: [Ar] 4s² 3d⁸
- For Ni²⁺: Remove 2 electrons from 4s, leaving 3d⁸.
- **Titanium (Ti)**: Atomic number = 22
- Electron configuration: [Ar] 4s² 3d²
- For Ti³⁺: Remove 2 electrons from 4s and 1 from 3d, leaving 3d¹.
- **Scandium (Sc)**: Atomic number = 21
- Electron configuration: [Ar] 4s² 3d¹
- For Sc³⁺: Remove 2 electrons from 4s and 1 from 3d, leaving no d-electrons.
- **Copper (Cu)**: Atomic number = 29
- Electron configuration: [Ar] 4s² 3d¹⁰
- For Cu⁺: Remove 1 electron from 4s, leaving 3d¹⁰.

3. **Count the Unpaired Electrons**:
- **Ni²⁺ (3d⁸)**:
- Configuration: ↑↓ ↑↓ ↑↓ ↑ ↑ (2 unpaired electrons)
- **Ti³⁺ (3d¹)**:
- Configuration: ↑ (1 unpaired electron)
- **Sc³⁺ (no d-electrons)**:
- Configuration: (0 unpaired electrons)
- **Cu⁺ (3d¹⁰)**:
- Configuration: ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ (0 unpaired electrons)

4. **Determine Color Presence**:
- Ions with unpaired d-electrons will typically exhibit color in solution.
- **Ni²⁺**: Colored (due to 2 unpaired electrons)
- **Ti³⁺**: Colored (due to 1 unpaired electron)
- **Sc³⁺**: Not colored (no unpaired electrons)
- **Cu⁺**: Not colored (no unpaired electrons)

5. **Conclusion**:
- The pairs that contain both colored ions in aqueous solution are Ni²⁺ and Ti³⁺. Sc³⁺ and Cu⁺ do not contribute to color due to the absence of unpaired d-electrons.

### Final Answer:
The pair of ions that are both colored in aqueous solution is **Ni²⁺ and Ti³⁺**.