Comment on the statement that elements of the first transition series posses many properties different form those of heavier transition elements.

Explanation

The heavier transition elements belong to fourth (4d), fifth (5d) and sixth (6d) transition series. Their properties are expected to be different from the elements belonging to the first (3d) series due to the following reasons :
(i) Atomic radii of heavier transition elements (4d- and 5d-series) are larger than those of the corresponding elements of the first transition series though those of 4d- and 5d-series are very close to each other.
(ii) Ionization enthalpies of 5d-series are higher than the corresponding elements of 3d- and 4d-series.
(iii) Enthalpies of atomisation of 4d- and 5d-series are higher than the corresponding elements of the first series.
(iv) Melting and boiling points of heavier transition elements are greater than those of the first transition series due to stronger inter-metallic bonding.