In this computational study, researchers examine the adsorption of superheavy elements Copernicium (Cn) and Flerovium (Fl), and their lighter homologs Mercury (Hg) and Lead (Pb), on a Selenium (100) surface. The approach employs periodic Density Functional Theory (DFT) using Quantum ESPRESSO (open-source suite of codes) with spin-orbit coupling and DFT-D4 dispersion correction. The results show that while a standard Perdew-Burke-Ernzerhof (PBE) setup (both functional and pseudopotential) captures the correct adsorption trend, a hybrid approach using the Perdew-Burke-Ernzerhof for solids (PBEsol) functional with PBEsol pseudopotentials for Se and PBE pseudopotentials for the adsorbates provides superior accuracy for adsorption energy values. We further probed the adsorbate-surface interactions and stability through density of states, charge transfer, and vibrational analysis.