Q.The element having least enthalpy of atomisation value in the first transition series is ______ (fill in the blank).

Enthalpy of Atomisation of Transition Metals

The enthalpy of atomisation is the energy needed to convert one mole of a solid metal into free gaseous atoms. For the transition metals this value is characteristically high, because their atoms are held together by very strong metallic bonding. The strength of that bonding depends on the number of unpaired d-electrons available for bonding: the more unpaired electrons an atom contributes to the metallic lattice, the stronger and more numerous the interatomic bonds, and the greater the enthalpy of atomisation.

Across a series the value therefore rises to a maximum near the middle, where the number of unpaired electrons peaks, and falls towards the ends. Chromium and the mid-series metals have among the highest values, while metals with few or no unpaired d-electrons available for bonding have low values. …