Compare the general characteristics of the first transition series of transition metals with those of the second and third transition series metals in the respective vertical columns. Give special emphasis on the following point :
(i) electronic configuration (ii) oxidation states (iii) inonisation enthalpies (iv) atomic sizes.

Explanation

(i) Electronif configuration. There are some exceptions in the electronic configurations. In all the three series.
(ii) Oxidation state. The elements belonging to the different series but present in the same group have similar electronic configuration and therefore, exhibit almost same variable oxidation state. In general, these are maximum in the middle of the series while minimum towards the end.
(iii) Ionisation enthalpies. In general, the ionisation enthalpies in all the three transition series increase from left to the right. However, the gaps in the two successive elements in a particular series are small and are also not regular. The first three ionisation enthalpies of the elements present in the first transition series are given in the text part. The `Delta_(i)H^(1)` values of the elements belonging to 5d series an higher as compared to those belonging to 3d to 4d series in the same group because of poor shelding by intervening 4f electrons present.
(iv) Atomic size. In all the three transition series, the atomic as well as ionic radii of the elements increase from left to the right. The values for 3d series are given in the text part. However, the increase in their values are not as much as expected since the shielding by (n-1)d electrons in not as much as expected. In a particular group, the atomic radius of the elements belonging to 4d series is more than the element in the 3d series. However, the gaps in the elements belonging to 4d and 5d series are negligible on account of lanthanoid contraction which the elements of 5d experience.