Linked from
The 18 pages that link to Relativistic effect, each with the reason it gives.
HalogenRelated: Such effects may alter the chemistry expected for the heaviest members of group 17.
Period 7 elementRelated: Relativistic effects alter orbital energies in the heaviest period 7 atoms.
UnbienniumRelated: Such effects would strongly influence any actual chemistry of element 129.
UnbioctiumBroader topic: Its magnitude in element 128 cannot be tested without atoms of the element.