In the series Sc (Z = 21) to Zn (Z = 30), the enthalpy of atomization of zinc is the lowest, i.e., 126 kJ mol−1. Why?
The extent of metallic bonding an element undergoes decides the enthalpy of atomization. The more extensive the metallic bonding of an element, the more will be its enthalpy of atomization. In all transition metals (except Zn, electronic configuration: 3d10 4s2), there are some unpaired electrons that account for their stronger metallic bonding. Due to the absence of these unpaired electrons, the inter-atomic electronic bonding is the weakest in Zn and as a result, it has the least enthalpy of atomization.
In 3d series from Sc to Zn, all elements have one or more unpaired e-1 s except Zn which has no unpaired electron as its outer EC is 3d104s2. Hence, the intermetallic bonding is weakest in zinc. Therefore, enthalpy of atomisation is lowest.
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