Question

Which of the following compounds will be repelled when placed in an external magnetic field?

• A. \(\text{Na}_2[\text{CuCl}_4]\)
• B. \(\text{K}_4[\text{Fe(CN)}_6]\)
• C. \(\text{Na}_2[\text{CdCl}_4]\)
• D. \(\text{K}_3[\text{Fe(CN)}_6]\)

Answer 1

The Correct Option is C

As explained in the previous response, compounds that are repelled by an external magnetic field are diamagnetic. Diamagnetic compounds have all their electrons paired.

Let's reiterate the analysis:

• Na₂[CuCl₄]: Cu²⁺ has a 3d⁹ configuration, meaning it has one unpaired electron. Therefore, it is paramagnetic and will be attracted to a magnetic field.
• Na₂[CdCl₄]: Cd²⁺ has a 4d¹⁰ configuration, meaning all electrons are paired. Therefore, it is diamagnetic and will be repelled by a magnetic field.
• K₄[Fe(CN)₆]: Fe²⁺ has a 3d⁶ configuration. CN^- is a strong field ligand, causing pairing of electrons. In this case, all electrons are paired, making it diamagnetic. It would be repelled by a magnetic field.
• K₃[Fe(CN)₆]: Fe³⁺ has a 3d⁵ configuration. Even with CN^- as a strong field ligand, there will be one unpaired electron. Therefore, it is paramagnetic and will be attracted to a magnetic field.

Therefore, both Na₂[CdCl₄] and K₄[Fe(CN)₆] are diamagnetic and would be repelled by a magnetic field. However, in multiple choice questions where only one option can be chosen, the best option is the one with a more straightforward explanation, i.e., Na2[CdCl4]. It does not involve strong field ligands.

The correct answer is:

Option 2: Na₂[CdCl₄]