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

Explanation

The given statement is true as explained below `:`
(i) Atomic radii of the 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) For first transition series, `+2` and `+3` oxidation states are more common whereas for heavier transition elements, higher oxidation states are more common( as discussed in Question)
(iii) Melting and boiling points of heavier transition elements are greater than those of the first transition series due to stronger intermetallic bonding ( M-M bonding) .
(iv) Ionization enthalpies of 5d series are higher than the corresponding elements of 3d and 4d series.
(vi ) The elements of the first transition series form low spin or high spin complexes depending upon the strength of the ligand field.However, the heavier transition elements form low spin complexes irrespective of the strength of the ligand field.