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.
Following a prediction by Smolańczuk [Phys. Rev. C 59, 2634 (1999)], we searched for superheavy element formation in the bombardment of 208 Pb with 449-MeV 86 Kr ions. We have observed three decay chains, each consisting of an implanted heavy atom and six subsequent a decays, correlated in time and position. In these decay chains, a rapid (ms) sequence of high energy a particles (E a $ 10 MeV) indicates the decay of a new high-Z element. The observed chains are consistent with the formation of 293 118 and its decay by sequential a-particle emission to 289 116, 285 114, 281 112, 277 110, 273 Hs (Z 108) and 269 Sg (Z 106). The production cross section is 2.2 12.6 20.8 pb.
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