Question

Why do transition metals have high enthalpies of atomization?

Answer 1

The metals having partially filled d-orbitals are known as transition metals. The enthalpy change involved when bonds in a compound break and the component atoms get reduced to individual atoms is known as the enthalpy of atomization.

Complete step by step answer:
The elements or metals that have partially filled d-orbitals are known as transition elements or metals. The valence shell electronic configuration of transition metals is $n{s^2}(n - 1)d$. The $n{s^2}$ electrons are the valence electrons.
The valence electrons result in the formation of strong metallic bonds between the transition metals. As the metallic bonds are stronger, a higher amount of energy is required to break the bonds between the transition metals. Thus, the enthalpy of atomization of transition metals is higher.
The net positive charge experienced by an electron in an atom is known as the effective nuclear charge. In the transition metals, more protons get added to the nucleus. Thus, the electrons experience a high positive charge.
A higher effective nuclear charge makes it difficult to break the component atoms of the transition metals. Thus, high energy is required to break the bonds between the transition metals. Thus, the enthalpy of atomization of transition metals is higher.
Thus, the transition metals have high enthalpies of atomization due to the two reasons: the presence of a large number of valence electrons and high effective nuclear charge.

Note:
The enthalpy of atomization increases as the number of valence electrons increases. The energy is supplied to break the metallic bonds. Thus, the value of enthalpy of atomization is always positive.