Magnetic Properties of d and f Block Elements - NEET Notes, Formula & Common Mistakes

What NEET Asks

• Identification: Questions on identifying paramagnetic or diamagnetic species based on electron configuration.
• Calculation: Direct application of the spin-only formula to calculate magnetic moment.
• Comparison: Comparing magnetic moments of different ions or correlating magnetic moment with the number of unpaired electrons.

Key Points

• Paramagnetism: Substances weakly attracted by magnetic fields, possessing one or more unpaired electrons. The more unpaired electrons, the stronger the paramagnetism.
• Diamagnetism: Substances weakly repelled by magnetic fields, having all electrons paired. They have zero magnetic moment.
• Origin: Magnetic properties primarily arise from the spin motion of electrons. Orbital motion is generally neglected for first-row transition metals in NEET calculations.
• Spin-Only Formula: Magnetic moment (μ) is calculated using μ = √n(n+2) BM, where 'n' is the number of unpaired electrons.
• d-Block Trends: Magnetic moment typically increases with 'n' up to d⁵ configuration, then decreases as electrons start pairing up.
• Lanthanoids: Exhibit strong paramagnetism due to well-shielded 4f electrons, and orbital contribution is significant.

Must-Know Formula / Reaction

Spin-only Magnetic Moment: μ = √n(n+2) BM

• μ: Magnetic moment in Bohr Magnetons (BM)
• n: Number of unpaired electrons

Common Mistakes

• Students often miscalculate the number of unpaired electrons for transition metal ions, especially when dealing with anomalous configurations or higher oxidation states.
• Don't confuse paramagnetism (unpaired electrons, attracted) with diamagnetism (all paired electrons, repelled).
• Students often forget to remove electrons from the outermost s-orbital first, before the d-orbital, when forming transition metal cations.

Rapid Revision

Paramagnetic species have unpaired electrons (n>0) and a non-zero magnetic moment (μ = √n(n+2) BM). Diamagnetic species have all paired electrons (n=0) and μ = 0 BM. Accurately determining 'n' from the ion's electronic configuration is key.