Question

Discuss the following property with respect to transition elements:

Melting and boiling points.

Answer 1

1. Transition elements have very high melting and boiling points compared to representative elements due to strong metallic bonds in their close-packed structures.
2. The metallic bonds have considerable covalent character because of overlapping unpaired d-electrons.
3. Melting and boiling points increase up to the middle of the series (around d⁵ configuration) as the number of unpaired electrons and hence bond strength increases.
4. After the middle, the number of unpaired electrons decreases due to electron pairing, causing a decrease in bond strength and melting/boiling points.
5. Elements like Zn, Cd, and Hg have low melting and boiling points due to the absence of unpaired electrons, making metallic bonding weaker.
6. Some anomalies, such as low melting points of Mn and Tc, are due to their complex lattice structures.