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The formation and the chemical characterization of single atoms of dubnium (Db, element 105), in the form of its volatile oxychloride, was investigated using the on‐line gas phase chromatography technique, in the temperature range 350–600 °C. Under the exactly same chemical conditions, comparative studies with the lighter homologues of Group 5 in the Periodic Table clearly indicate the volatility sequence being NbOCl3 > TaOCl3 ≥ DbOCl3. From the obtained experimental results, thermochemical data for DbOCl3 were derived. The present study delivers reliable experimental information for theoretical calculations on chemical properties of transactinides., Dubnium obeys Mendeleev's periodicity. Fifty years after the discovery of this element, its chemical behavior was experimentally revisited. From the gas chromatographic investigation of the volatile oxychloride compound, a trend of decreasing volatility along Group 5 elements was deduced, in agreement with the expectations by the laws established in the Periodic Table.

Structures of a trivalent actinium cation in helium clusters (Ac3+ ⋅Hen ) have been studied by quantum path integral molecular dynamics simulations with different cluster sizes, n=18-200. The nuclear quantum effect of helium atoms plays an important role in the vibrational amplitude of the Ac3+ -He complex at low temperatures (1-3 K) at which the complex is stable. We found that the coordination number of helium atoms comprising the first solvation shell can be as high as eighteen. In this case, the helium atoms are arranged in D4d symmetry. The Ac3+ -He18 complex becomes more rigid as the cluster increases in size, which implies that it becomes more stable. The simulation results are based on an accurate description of the Ac3+ -He interaction using relativistic ab initio calculations.