Manifestation of relativistic effects in the chemical properties of nihonium and moscovium revealed by gas chromatography studies

Chemical reactivity of the superheavy elements nihonium (Nh, element 113) and moscovium (Mc, element 115) has been studied by the gas-solid chromatography method using a new combined chromatography and detection setup. The Mc isotope, ²⁸⁸Mc, was produced in the nuclear fusion reaction of ⁴⁸Ca ions with ²⁴³Am targets at the GSI Helmholtzzentrum Darmstadt, Germany. After isolating ²⁸⁸Mc ions in the gas-filled separator TASCA, adsorption of ²⁸⁸Mc and its decay product ²⁸⁴Nh on silicon oxide and gold surfaces was investigated. As a result of this work, the values of the adsorption enthalpy of Nh and Mc on the silicon oxide surface were determined for the first time, −∆H_ads^SiO2(Mc)=54₋₅⁺¹¹ kJ/mol and −∆H_ads^SiO2(Nh)=58₋₃⁺⁸ kJ/mol (68% c.i.). The obtained −ΔH_ads values are in good agreement with results of advanced relativistic calculations. Both elements, Nh and Mc, were shown to interact more weakly with the silicon oxide surface than their lighter homologues Tl and Bi, respectively. However, Nh and Mc turned out to be more reactive than the neighbouring closed-shell and quasi-closed-shell elements copernicium (Cn, element 112) and flerovium (Fl, element 114), respectively. The established trend is explained by the influence of strong relativistic effects on the valence atomic orbitals of these elements.