Question

Which of the following ions shows the highest spin-only magnetic moment value?

Hint:

The {spin-only magnetic moment} depends on the number of {unpaired electrons}. The greater the unpaired electrons, the higher the magnetic moment.

Answer 1

Step 1: Understanding Magnetic Moment 
The spin-only magnetic moment (\( \mu_s \)) of an ion is calculated using the formula: \[ \mu_s = \sqrt{n(n+2)} { BM} \] where \( n \) is the number of unpaired electrons. 
Step 2: Electronic Configuration of \( {Mn}^{2+} \) 
- The atomic number of manganese (Mn) is 25.
- Its electronic configuration: \( [{Ar}] 3d^5 4s^2 \).
- For \( {Mn}^{2+} \) (after losing two electrons from \( 4s^2 \)): \( [{Ar}] 3d^5 \).
- Since \( 3d^5 \) has all unpaired electrons, \( n = 5 \). 
Step 3: Calculation of Magnetic Moment 
Substituting \( n = 5 \) into the formula: \[ \mu_s = \sqrt{5(5+2)} = \sqrt{35} \approx 5.92 { BM} \] 
Step 4: Conclusion 
Among the given ions, \( {Mn}^{2+} \) has the highest spin-only magnetic moment of 5.92 BM due to the presence of five unpaired electrons.