Question

Which of the following compounds can be coloured?

• A. Ag$_2$SO$_4$
• B. CuF$_2$
• C. Cu$_2$Cl$_2$
• D. MgF$_2$

Hint:

Transition metal compounds often exhibit colour due to the presence of partially filled d-orbitals that allow electronic transitions.

Answer 1

The Correct Option is B

Step 1: Understand the factors for colouration.
Compounds can be coloured if they have partially filled d-orbitals, which allow the absorption of light in the visible spectrum. The transition metal compounds are typically the ones that can exhibit such properties.
Step 2: Apply to the options.
- Ag$_2$SO$_4$ and MgF$_2$ are both ionic and do not have partially filled d-orbitals, so they are colourless. - CuF$_2$ is a transition metal compound and can exhibit colour due to the partially filled 3d orbitals of copper.
Step 3: Conclude the correct answer.
The only coloured compound among the options is CuF$_2$, so option (B) is correct.
Final Answer: \[ \boxed{\text{CuF}_2} \]