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Question
Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following point:
Ionisation enthalpies
Solution
In every series, the first ionization enthalpy generally increases gradually as we move from left to right, although some exceptions are observed in every series. In the same horizontal group, the first ionization enthalpy of some elements of 4d series is higher and that of some elements is lower as compared to the elements of 3d series, although the first ionization enthalpy of 5d series is higher as compared to 3d and 4d series. The reason for this is the weak shielding effect of the nucleus on the 4f electrons in the 5d series.
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