Which of the following compounds is expected to be coloured?

Options

A. `Ag_2SO_4`
B. `CuF_2`
C. `MgF_2`
D. `CuCl`

Explanation

To determine which of the given compounds is expected to be colored, we need to analyze the oxidation states and electronic configurations of the metal ions in each compound. The color in transition metal compounds arises from the presence of unpaired electrons in their d-orbitals.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are CuCl, CuF2, MgCl2, and Ag2.

2. **Determine the Oxidation States**:
- **CuCl**: Copper is in the +1 oxidation state (Cu+).
- **CuF2**: Copper is in the +2 oxidation state (Cu2+).
- **MgCl2**: Magnesium is in the +2 oxidation state (Mg2+).
- **Ag2**: Silver is in the +1 oxidation state (Ag+).

3. **Identify the Electronic Configurations**:
- **Copper (Cu)**: The electronic configuration is [Ar] 4s² 3d⁹ (for Cu) and [Ar] 3d¹⁰ (for Cu+).
- **Cu+ (in CuCl)**: Loses one 4s electron, resulting in [Ar] 3d¹⁰. This has no unpaired electrons, hence it is colorless.
- **Cu2+ (in CuF2)**: Loses both 4s electrons and one 3d electron, resulting in [Ar] 3d⁹. This has one unpaired electron, hence it is colored.
- **Magnesium (Mg)**: The electronic configuration is [Ne] 3s². Since it is an alkaline earth metal, it has no unpaired electrons and is colorless.
- **Silver (Ag)**: The electronic configuration is [Kr] 4d¹⁰ 5s¹.
- **Ag+ (in Ag2)**: Loses one 5s electron, resulting in [Kr] 4d¹⁰. This has no unpaired electrons, hence it is colorless.

4. **Conclusion**: Among the compounds analyzed, only CuF2 (with Cu2+) has unpaired electrons and is expected to be colored.

### Final Answer:
The compound expected to be colored is **CuF2**.

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