Question

Why is the increase in the first ionisation energy of transition elements not very regular with increase in atomic number?

Answer 1

1. Transition metals have close-packed structures with strong metallic bonds holding atoms together.
2. These metallic bonds have considerable covalent character due to unpaired d-electrons.
3. A greater number of unpaired d-electrons means stronger metallic bonds and hence higher boiling points.
4. Boiling points increase up to the middle of the d-block series (d⁵ configuration), where unpaired electrons are maximum.
5. More energy is required to break these strong bonds, resulting in higher boiling points than other elements.