The last element of the third transition series is

La (atomic number 57) and the elements $Hf$ (atomic number 72) through Hg make up the 5d-series (atomic number 80). These components belong to the sixth period. Electronically, it is set up as $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{s}}^2$.

The following is a list of the complete and valence-shell electronic configurations of an element's 5d-series atom. In this case, $\left[\mathrm{Xe}\right]$54 = 2, 8, 18, 18, (five–shells).