2.3.3 Transition Metals
Understanding the role of d-electrons in metallic bonding.
Delocalized d-electrons
For s-block metals (like Calcium), only the s-electrons are delocalized. However, **transition metals** can delocalize electrons from both their **4s** and **3d** subshells.
Key Implication: Because 3d electrons can also participate in the metallic bond, there are significantly more delocalized electrons holding the lattice together compared to Group 1 or 2 metals.
Case Study: Calcium vs. Scandium
Calcium (Group 2)
- Config: [Ar] 4s²
- Delocalized: 2 electrons (4s only)
- Melting Point: ~842°C
Scandium (Transition)
- Config: [Ar] 3d¹ 4s²
- Delocalized: 3 electrons (4s + 3d)
- Melting Point: ~1541°C
The involvement of the 3d electron nearly doubles the melting point.
Electrical Conductivity
While transition metals are excellent conductors, more delocalized electrons does not always mean better conductivity than s-block metals.
For example, **Silver** and **Copper** are the best conductors, but **Iron** (with many d-electrons) is relatively resistive. This is because the d-electrons can also contribute to scattering effects in the lattice, impeding flow. However, for the purpose of standard exam questions, simply stating they are "good conductors due to delocalized electrons" is sufficient.