Question

In the series $Sc(Z=21)$ to $Zn(Z=30)$, the enthalpy of atomization of which element is least?
A) $Sc$
B) $Mn$
C) $Cu$
D) $Zn$

Answer 1

Most of the transition metals have unpaired electrons due to which they show stronger metallic character, meaning, they easily lose an electron or two in order to gain positive oxidation state which makes them more stable.
The transition metals which don't have unpaired electrons would have comparatively lower enthalpy of atomization because it would be easier to break the metal-metal bonds, as they would be weaker than the others.

Complete answer:
Every spontaneous process has a tendency to lead to the formation of different products. Out of all the methods which are known to us, some of them are known to absorb energy while the others result in release of enthalpy. Hence, we always tend to experience a change in energy upon progression of the methods. This change observed in terms of enthalpy can be because of the enthalpy of atomization.
Enthalpy of atomization which is denoted by the symbol, ${{\Delta }_{a}}{{H}^{0}}$, can be defined as the change observed in the energy when one mole of the bond is entirely broken in order to obtain atoms in the gaseous phase. For instance, atomization of methane molecules. The reaction can be chemically represented by the following equation,
$C{{H}_{4}}~\left( g \right){ }\to ~C{ }\left( g \right){ }+{ }4H{ }\left( g \right)$
${{\Delta }_{a}}{{H}^{0}}={ }1665.0{ }kJ{ }mo{{l}^{-1}}$
The value of enthalpy of atomization is mentioned in front of the equation.
In case of the diatomic molecules, the value of enthalpy of atomization is found to be equal to the value of enthalpy of bond dissociation. For instance atomization of hydrogen molecule, which can be expressed in the form of chemical equation as,
${{H}_{2~}}\left( g \right)\to 2H\left( g \right)$ ${{\Delta }_{a}}{{H}^{0}}={ }435.0{ }kJ{ }mo{{l}^{-1}}$
Now if we consider both the metals which are given in the question, the zinc and scandium both belong to the same group which is the third group present in the periodic table. The enthalpy of atomization is decided by the extent of the metallic bonding which is shown by an element. With increase in metallic character, the enthalpy of atomization increases. All the transition metals contain some unpaired electrons which are responsible for the stronger metallic bonding. But, in zinc, there is absence of these unpaired electrons hence it has lower inter-electronic attractions between the atoms of zinc, which ultimately results in least enthalpy of atomization.

Hence the correct option would be option D.

Note: The zinc does not have any unpaired electrons so it cannot lose its electron in order to form metallic bonds, unlike the other members of the transition group. This results in lower enthalpy of atomization of zinc, as the bonds between the zinc atoms are weak, and it requires lower energy to break them.