Sc (Z = 21) to Zn (Z = 30) belong to the fourth period of the periodic table. The degree of metallic bonding an element undergoes influences the atomization enthalpy. The more extensive an element’s metallic bonding is, the more its atomization enthalpy would be. The presence of some unpaired electrons in all transition metals with the exception of Zn, explains why their metallic bonds are stronger. Zn has the lowest enthalpy of atomization because it lacks these unpaired electrons, which weakens the inter-atomic electrical connection.