Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements

cbse
dandf-blockelements

#1

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) Ionisation 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 intermetallic bonding.
(v) The elements of the first transition series generally form low spin or high spin complexes depending upon the strength of ligand field. However, the heavier transition elements form low spin complexes irrespective of the strength of the ligand field