Question

Why do the transition elements have higher enthalpies of atomization? In $3d$ series ($Sc$ to $Zn$), which element has the lowest enthalpy of atomization and why?

Answer 1

Transition metals have high effective nuclear charge and in addition, they possess very large no. of valence electrons. Due to these available valence electrons, they form strong metallic bonds. So, the enthalpy of atomization of transition element is high.

In case of 3rd transition series, all the transition elements (except Zn), possess some unpaired electrons that accounts for their stronger metallic bonding.

Since, in Zn (electronic configuration: [Ar] 3d${}^{10}$4s${}^2$ ), no unpaired e${}^{-}$ s are present so, the interatomic electronic bond is weakest and consequently, it has the least enthalpy of atomization.

Enthalpy of atomization: is the enthalpy change when one mole of bonds is completely broken to obtain atoms in the gas phase.