Question

Why 2nd transition series is more than 1st transition series?

Answer 1

In first transition series, electrons are filled only in d orbitals but in second and third transition series, electrons are filled in d- and f-orbitals. So nuclear charge experienced by valence electrons in second and third transition series is more than that of the first transition series.

Answer 2

Answer:

The atomic volume of the transition elements are low because the electrons are added in (n-1)d subshell and not in ns subshell.Therefore, the increased nuclear charge is partially screened by d-electrons and the outer electrons are strongly attracted by the nucleus.as a result, the densities of transition elements are higher.