The aqueous solution containing which one of the following ions will be colourless
(Atomic number `Sc = 21, Fe = 26, Ti = 22, Mn = 25)`

Options

A. `Sc^(3+)`
B. `Fe^(2+)`
C. `Ti^(3+)`
D. `Mn^(2+)`

Explanation

To determine which aqueous solution containing the given ions will be colorless, we need to analyze the electronic configurations of each ion and check for the presence of unpaired electrons. A solution is considered colorless if the ion has no unpaired electrons.

### Step-by-Step Solution:

1. **Identify the Ions and Their Atomic Numbers:**
- Scandium (Sc) with atomic number 21
- Iron (Fe) with atomic number 26
- Titanium (Ti) with atomic number 22
- Manganese (Mn) with atomic number 25

2. **Determine the Electronic Configuration of Each Element:**
- **Scandium (Sc):**
- Electronic configuration: \( \text{[Ar]} 4s^2 3d^1 \)
- **Iron (Fe):**
- Electronic configuration: \( \text{[Ar]} 4s^2 3d^6 \)
- **Titanium (Ti):**
- Electronic configuration: \( \text{[Ar]} 4s^2 3d^2 \)
- **Manganese (Mn):**
- Electronic configuration: \( \text{[Ar]} 4s^2 3d^5 \)

3. **Calculate the Electronic Configuration for Each Ion:**
- **Scandium Ion (Sc³⁺):**
- Remove 3 electrons: \( \text{[Ar]} \) (0 from 4s and 1 from 3d)
- Configuration: \( \text{[Ar]} \) (0 unpaired electrons)
- **Iron Ion (Fe²⁺):**
- Remove 2 electrons: \( \text{[Ar]} 3d^6 \) (0 from 4s)
- Configuration: \( \text{[Ar]} 3d^6 \) (4 unpaired electrons)
- **Titanium Ion (Ti³⁺):**
- Remove 3 electrons: \( \text{[Ar]} 3d^1 \) (2 from 4s and 1 from 3d)
- Configuration: \( \text{[Ar]} 3d^1 \) (1 unpaired electron)
- **Manganese Ion (Mn²⁺):**
- Remove 2 electrons: \( \text{[Ar]} 3d^5 \) (0 from 4s)
- Configuration: \( \text{[Ar]} 3d^5 \) (5 unpaired electrons)

4. **Determine Color or Colorlessness:**
- **Scandium (Sc³⁺):** Colorless (0 unpaired electrons)
- **Iron (Fe²⁺):** Colored (4 unpaired electrons)
- **Titanium (Ti³⁺):** Colored (1 unpaired electron)
- **Manganese (Mn²⁺):** Colored (5 unpaired electrons)

5. **Conclusion:**
- The only ion that results in a colorless solution is **Scandium (Sc³⁺)**.

### Final Answer:
The aqueous solution containing **Scandium ion (Sc³⁺)** will be colorless.

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