Which element from following is the last element of 5d-transition series?

The 5d transition series consists of the elements from Lanthanum (La, atomic number 57) to Mercury (Hg, atomic number 80). This series comprises a portion of the d-block elements, specifically those wherein the d-electron shell is being filled progressively.
\(\mathrm{H g}\) (Mercury) is the last element of this series, with an atomic number of 80. Its electron configuration is \([X e] 4 f^{14} 5 d^{10} 6 s^2\).
Elements in the 5d series span across the periodic table and are found prominently in groups commonly referred to as the transition metals. Mercury is well-known for being the only metal that is liquid at room temperature.
Understanding the periodic table's structure and where the d-block elements are located helps clarify configurations and series order and facilitates identification of such elements without much confusion.