Interactions of single atoms of element 120 (E120) and its lighter homologs (Ba and Ra) with the stable gold (111) surface simulated by clusters are studied using relativistic density functional theory and accurate two-component shape-consistent small-core pseudopotentials. The predicted E120 adsorption energy on gold (ca. 250 kJ mol^-1) is significantly larger than the previously reported value. The trends in interactions of heavy group 2 elements with gold are discussed on the basis of electronic structure calculations and estimates by the semiempirical macroscopic Eichler-Miedema model.