Comment on the statement that elements of first transition series possess many properties different fromt those of the havier transition elements.

Explanation

The havier transition elements belong to fourth (4d) and 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) The atomic radii of the elements belonging ot 4d and 5d series are more due to greate number of electron shells. However, the difference in 4d and 5d transition elements are comparatively less because of lanthaoid contraction.
(ii) Because of stronger inter atomic bonding , the m.p and b.p. of the element of 4d and 5d series are higher.
(iii) Ionisation enthalpies are expected to decrease as we move from one series to the other. However, the values for the elements of 5d series are higher as compared to the elements belonging to the other two series due to lanthanoid contraction.
Actually atomic size decreases on account of it and effective nuclear charge increases. As a result , there is an increase in ionisation energy in case of 3d elements.