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The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes (269)Hs (refs 8, 9) and (270)Hs (ref. 10) in the fusion reaction between (26)Mg and (248)Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO(4), for which we determine an enthalpy of adsorption on our detector surface that is comparable to the adsorption enthalpy determined under identical conditions for the osmium oxide OsO(4). These results provide evidence that the chemical properties of hassium and its lighter homologue osmium are similar, thus confirming that hassium exhibits properties as expected from its position in group 8 of the periodic table.

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Fully relativistic (four-component) density-functional theory calculations were performed for elements 112 and 114 and their lighter homologs, Hg and Pb, interacting with gold systems, from an atom to a Au(n) cluster simulating the Au(111) surface. Convergence of the adatom-metal cluster binding energies E(b) with cluster size was reached for n>90. Hg, Pb, and element 114 were found to preferably adsorb at the bridge position, while element 112 was found to preferably adsorb at a hollow site. Independently of the cluster size, the trend in E(b) is Pb>>114>Hg>112. The obtained E(b) for Pb and element 112 are in good agreement with the measured adsorption enthalpies of these elements on gold, while the Hg value is obviously underestimated, confirming the observation that adsorption takes place not on the surface but in it. A comparison of chemical bonding in various systems shows that element 114 should be more reactive than element 112: A relative inertness of the latter is caused by the strong relativistic stabilization of the 7s atomic orbital. On the contrary, van der Waals bonding in element 114 systems should be weaker than in those of element 112 due to its larger radius.

The interaction of elements 112 and 114 with inert surfaces has been studied on the basis of fully relativistic ab initio Dirac-Coulomb CCSD(T) calculations of their atomic properties. The calculated polarizabilities of elements 112 and 114 are significantly lower than corresponding Hg and Pb values due to the relativistic contraction of the valence ns and np(12) orbitals, respectively, in the heavier elements. Due to the same reason, the estimated van der Waals radius of element 114 is smaller than that of Pb. The enthalpies of adsorption of Hg, Pb, and elements 112 and 114 on inert surfaces such as quartz, ice, and Teflon were predicted on the basis of these atomic calculations using a physisorption model. At the present level of accuracy, -DeltaH(ads) of element 112 on these surfaces is slightly (about 2 kJ/mol) larger than -DeltaH(ads)(Hg). The calculated -DeltaH(ads) of element 114 on quartz is about 7 kJ/mol and on Teflon is about 3 kJ/mol smaller than the respective values of -DeltaH(ads)(Pb). The trend of increasing -DeltaH(ads) in group 14 from C to Sn is thus reversed, giving decreasing values from Sn to Pb to element 114 due to the relativistic stabilization and contraction of the np(12) atomic orbitals. This is similar to trends shown by other atomic properties of these elements. The small difference in DeltaH(ads) of Pb and element 114 on inert surfaces obtained within a picture of physisorption contrasts with the large difference (more than 100 kJ/mol) in the chemical reactivity between these elements.

The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine.

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Adsorption energies of superheavy elements (SHEs) Cn, Nh, and Fl and their lighter homologues Hg, Tl, and Pb, respectively, on a Au(111) surface at different adsorbate coverages are predicted via periodic relativistic DFT calculations with the aim of assisting the outcome of related "one-atom-at-a-time" gas-phase chromatography experiments. In agreement with previous DFT studies with the use of a cluster model, the present results for large supercells are indicative of high volatility of Cn. Thus, this element should not interact with the regular Au(111) surface at room temperature but should adsorb on it in a vacancy. Fl should moderately interact with such a surface under ambient conditions, while Nh should be the most reactive element with respect to gold. All three elements should, however, reveal much lower reactivity toward gold than their lighter homologues. The reasons for this are the strong relativistic stabilization and contraction of the 7s and 7p AOs. The obtained trend in the adsorption energy, Nh ≫ Fl > Cn, enables one to easily separate these elements from each other, as well as from their lighter homologues using gold or gold/quartz surfaces.