Question

Why do the transition elements exhibit higher entalpies of atomisation ?

Answer 1

Transition element has high effective nuclear charge and a large number of valance electrons. Therefore, they form very strong metallic bonds or metal. Metallic bonding which arises due to unpaired $e^{-}$ in the $(n-1)d$ subshell. As a result, the enthalpy of atomisation of transition element is high.