Question

Which of the following ion has highest magnetic moment value?

• A. \( \mathrm{Cr^{2+}} \)
• B. \( \mathrm{Ni^{2+}} \)
• C. \( \mathrm{Cu^{2+}} \)
• D. \( \mathrm{Co^{3+}} \)

Hint:

Magnetic moment depends on number of unpaired electrons. More unpaired electrons means higher magnetic moment.

Answer 1

The Correct Option is A

Step 1: Use formula for magnetic moment.
Magnetic moment is given by the spin-only formula:
\[ \mu = \sqrt{n(n+2)}\ \text{BM} \] where \(n\) is the number of unpaired electrons. Greater the number of unpaired electrons, higher is the magnetic moment.
Step 2: Find unpaired electrons in each ion.

• \( \mathrm{Cr^{2+}} \): Electronic configuration \(3d^4\), so it has 4 unpaired electrons.
• \( \mathrm{Ni^{2+}} \): Configuration \(3d^8\), has 2 unpaired electrons.
• \( \mathrm{Cu^{2+}} \): Configuration \(3d^9\), has 1 unpaired electron.
• \( \mathrm{Co^{3+}} \): Configuration \(3d^6\), usually has fewer unpaired electrons (often low spin).

Step 3: Compare magnetic moments.
Since \( \mathrm{Cr^{2+}} \) has the highest number of unpaired electrons (4), it will have the highest magnetic moment.
Step 4: Conclusion.
Therefore, \( \mathrm{Cr^{2+}} \) shows the maximum magnetic moment.
Final Answer:\( \mathrm{Cr^{2+}} \).