Thermochemical and Physical Properties of Element 112

Abstract

The high nuclear charges of the heaviest elements influence their electronic structure and hence their chemical properties. [1][2][3][4][5] The experimental results so far obtained for the heaviest chemically investigated elements reveal that seaborgium, [6,7] bohrium, [8] and hassium [9] behave as typical representatives of the corresponding Group 6, 7, and 8 of the periodic table. Apparently, relativistic effects do not introduce a perceptible destabilization of the highest oxidation states of these elements in the chemical environments they have been studied in. An even stronger increase of relativistic effects is predicted for the transactinides of Groups 12-18. [1][2][3] Element 112, a representative of Group 12 of the periodic table, has a predicted closed-shell electronic ground-state configuration of [Rn]5f 14 6d 10 7s 2 , rendering this element one of the key elements regarding relativistic effects in the electronic structure. [3,5,10] Recently, our gas chromatography experiments with only two observed atoms of element 112 revealed evidence for a metallic adsorption interaction with the stationary gold surface. [11] Here we present new experimental results with an increased number of observed atoms that confirm these observations and improve their statistical significance. From the complete data set, thermochemical and physical data are deduced for element 112 and compared to the corresponding properties of its homologues in Group 12: Zn, Cd, and Hg. The increased stabilization of the atomic state of element 112 reveals a further enhancement of the relativistic effects with increasing atomic number Z in Group 12.For element 112 a noble-metallic character was predicted from empirical extrapolations. [12,13] Relativistic atomic calculations revealed a contraction of the spherical 7s orbitals, leading to the prediction of an enhanced stability of the elemental atomic state for element 112. Accordingly, a noblegas-like behavior was postulated. [14] Modern calculation methods confirmed a stronger binding of the 7s orbitals. [3] However, the spin-orbit coupling of the 6d orbitals is predicted to lead to an electronic ground state configuration with a 6d 5/2 orbital that is similar energetically and spatially to the 7s orbital, indicating that element 112 could be a noble transition metal [5,15] or even a semiconductor. [16] Based on these strongly differing predictions, it is decisive for experimentalists to be able to distinguish in chemical experiments whether element 112 behaves more as a noble metal or as a noble gas. Therefore, investigation of gas adsorption properties of element 112 on metal surfaces has been suggested. [17] In such studies the energy content of the adsorption bond between element 112 and the metallic stationary phase, the standard adsorption enthalpy at zero surface coverage (DH ads Au ), is determined. This quantity differentiates between metal-bond formation and weak van der Waals physisorption interaction. The semiempirical macroscopic adsorption model based on the Miedema approach ...

Chemistry of superheavy elements

“…[250]. This strongly supports the above mentioned conclusion about the high volatility of Cn and its metallic character expressed in a clear -but weaker than Hg -metal-metal bond formation with Au.…”

“…This chemistry experiment was the first and independent confirmation of nuclear decay chains reported earlier from FLNR experiments about the synthesis of element 287 114 and 291 116 [32,35]. A third experiment [250] was carried out with a higher gas-flow rate which yielded two atoms of 283 Cn deposited at −29 • C and −39…”

Communications: Adsorption of element 112 on the gold surface: Many-body wave function versus density functional theory

“…3, 5, and 8͒ are systematically lower than their counterparts derived from thermochromatographic data ͑0.54 −3 +4 eV͒. 2 A more serious discrepancy between theoretical and experimental data consists in different ordering of adsorption energies for Cn and element 114 ͑E114͒. The results of thermochromatograpic registration of these two elements belonging to the same decay chain indicate that Cn is much better adsorbed on a gold surface than E114.…”

Prediction of the thermal release of transactinide elements (112 ≤Z≤ 116) from metals

“…Miedema [19] was employed to calculate enthalpies of solid solution at infinite small concentrations (ΔH Sol ) using a set of parameters for SHE taken from [18] (except the values from Cn* which we deduced using latest experimental adsorption data of Cn on Au [20]). Table 1 collects the used Miedema parameters which are specific for the SHE under investigation.…”

“…The resulting ΔH Sol together with the sublimation enthalpy (ΔH Subl given in literature, e.g. [20][21][22]) yields the release enthalpy (ΔH f ), according to Eq. (1).…”