Question

How does the paramagnetic character of the bivalent ions of first transition metal series vary from titanium (Z = 22) to copper (Z = 29)?

Answer 1

1. The paramagnetic character of the bivalent ions of the first transition metal series (from titanium, Z = 22, to copper, Z = 29) varies according to the number of unpaired electrons present in their 3d orbitals.
2. Paramagnetism arises due to the presence of unpaired electrons, which generate magnetic moments.
3. As we move from Ti²⁺ to Mn²⁺, the number of unpaired electrons increases from two in Ti²⁺ (3d²) to five in Mn²⁺ (3d⁵).
4. This leads to a corresponding increase in paramagnetic character, with Mn²⁺ showing the maximum paramagnetism.
5. Beyond Mn²⁺, from Fe²⁺ to Cu²⁺, the number of unpaired electrons decreases from four in Fe²⁺ (3d⁶) to one in Cu²⁺ (3d⁹). Therefore, the paramagnetic character decreases in this portion of the series. 
6. Hence, the paramagnetic behaviour first increases and then decreases across the series, reaching its peak at Mn²⁺, where the maximum number of unpaired electrons (five) is observed.