The elements with the highest and the lowest enthalpy of atomisation respectively, for first row transition elements are:

The enthalpy of atomisation is the enthalpy change that accompanies the total separation of all atoms in a chemical substance.

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 atomisation.

$\mathrm{Sc}$ has the lowest enthalpy of atomisation, for first row of transition elements and $\mathrm{Zn}$ $(4{\mathrm{d}}^{10} 5{\mathrm{s}}^2)$ has completely filled $\mathrm{d}-$orbital and has no unpaired electron to take part in the formation of metallic bonds. So, the metallic bonding in zinc is the weakest and it has the least enthalpy of atomisation.