Question

Which one of the ions Fe$^{2+}$ and Fe$^{3+}$ is more paramagnetic and why?

Hint:

Maximum paramagnetism occurs when d-orbitals are half-filled (d$^5$).

Answer 1

Step 1: Electronic configuration.
- Fe atom: [Ar] 3d$^6$ 4s$^2$
- Fe$^{2+}$: [Ar] 3d$^6$
- Fe$^{3+}$: [Ar] 3d$^5$
Step 2: Count unpaired electrons.
- Fe$^{2+}$ (3d$^6$): 4 unpaired electrons.
- Fe$^{3+}$ (3d$^5$): 5 unpaired electrons.
Step 3: Paramagnetism.
Paramagnetism depends on the number of unpaired electrons. More unpaired electrons → higher paramagnetism.
Conclusion:
Fe$^{3+}$ is more paramagnetic than Fe$^{2+}$ because it has 5 unpaired electrons compared to 4 in Fe$^{2+}$.