Which of the following ions does not give coloured solution ?

Options

A. `Fe^(2+)`
B. `Zn^(2+)`
C. `Cr^(3+)`
D. `Mn^(2+)`

Explanation

To determine which of the following ions does not give a colored solution, we need to analyze the electronic configurations of the given ions. The presence of unpaired electrons in the d-orbitals of transition metals is what typically leads to colored solutions. If there are no unpaired electrons, the solution will be colorless.

### Step-by-Step Solution:

1. **Identify the Ions**: The ions we need to analyze are:
- Fe²⁺
- Zn²⁺
- Cr³⁺
- Mn²⁺

2. **Determine the Electronic Configuration of Each Ion**:
- **Fe²⁺**:
- Atomic number of Fe = 26
- Ground state electronic configuration: [Ar] 3d⁶ 4s²
- For Fe²⁺, we lose 2 electrons (from 4s and 3d): [Ar] 3d⁶
- In 3d⁶, there are 4 unpaired electrons (according to Hund's rule).
- **Conclusion**: Fe²⁺ gives a colored solution.

- **Zn²⁺**:
- Atomic number of Zn = 30
- Ground state electronic configuration: [Ar] 3d¹⁰ 4s²
- For Zn²⁺, we lose 2 electrons (from 4s): [Ar] 3d¹⁰
- In 3d¹⁰, there are no unpaired electrons.
- **Conclusion**: Zn²⁺ does not give a colored solution (colorless).

- **Cr³⁺**:
- Atomic number of Cr = 24
- Ground state electronic configuration: [Ar] 3d⁵ 4s¹
- For Cr³⁺, we lose 3 electrons (2 from 4s and 1 from 3d): [Ar] 3d³
- In 3d³, there are 3 unpaired electrons.
- **Conclusion**: Cr³⁺ gives a colored solution.

- **Mn²⁺**:
- Atomic number of Mn = 25
- Ground state electronic configuration: [Ar] 3d⁵ 4s²
- For Mn²⁺, we lose 2 electrons (from 4s): [Ar] 3d⁵
- In 3d⁵, there are 5 unpaired electrons.
- **Conclusion**: Mn²⁺ gives a colored solution.

3. **Final Conclusion**:
- Among the ions analyzed, **Zn²⁺** is the only ion that does not have unpaired electrons and therefore does not give a colored solution.

### Answer:
**Zn²⁺ does not give a colored solution.**