Seaborgium

Abstract: The quest for superheavy elements (SHEs) is driven by the desire to find and explore one of the extreme limits of existence of matter. These elements exist solely due to their nuclear shell stabilization. All 15 presently 'known' SHEs (11 are officially 'discovered' and named) up to element 118 are short-lived and are man-made atom-at-a-time in heavy ion induced nuclear reactions. They are identical to the transactinide elements located in the seventh period of the periodic table beginning with rutherfordium (element 104), dubnium (element 105) and seaborgium (element 106) in groups 4, 5 and 6, respectively. Their chemical properties are often surprising and unexpected from simple extrapolations. After hassium (element 108), chemistry has now reached copernicium (element 112) and flerovium (element 114). For the later ones, the focus is on questions of their metallic or possibly noble gas-like character originating from interplay of most pronounced relativistic effects and electron-shell effects. SHEs provide unique opportunities to get insights into the influence of strong relativistic effects on the atomic electrons and to probe 'relativistically' influenced chemical properties and the architecture of the periodic table at its farthest reach. In addition, they establish a test bench to challenge the validity and predictive power of modern fully relativistic quantum chemical models.

Abstract: Life is short for the heaviest elements. They emerge from high-energy nuclear collisions with scant time for detection before they break up into lighter atoms. Even et al. report that even a few seconds is long enough for carbon to bond to the 106th element, seaborgium (see the Perspective by Loveland). The authors used a custom apparatus to direct the freshly made atoms out of the hot collision environment and through a stream of carbon monoxide and helium. They compared the detected products with theoretical modeling results and conclude that hexacarbonyl Sg(CO)6 was the most likely structural formula. Science , this issue p. [1491][1]; see also p. [1451][2] [1]: /lookup/doi/10.1126/science.1255720 [2]: /lookup/doi/10.1126/science.1259349

Abstract: For the first time, chemical separations of element 106 (Seaborgium, Sg) were performed in aqueous solutions. The isotopes Sg and Sg were produced in the Cm + Ne reaction at a beam energy of 121 MeV. The reaction products were continuously transported by a He(KCl)-jet to the computer-controlled liquid chromatography system ARCA. In 0.1 M HNO3/5 X ΙΟ -4 M HF, Sg was found to be eluted within 10 s from 1.6X8 mm cation-exchange columns (Aminex A6, 17.5±2 μπι) together with the hexavalent Moand W-ions, while hexavalent U-ions and tetravalent Zr-, Hf-, and element 104 ions were strongly retained on the column. Element 106 was detected by measuring correlated α-decays of the daughter isotopes 78-s 104 and 26-s 102. For the isotope Sg, we have evidence for a spontaneous fission branch. It yields a partial spontaneousfission half-life which is in agreement with recent theoretical predictions. The chemical results show that the most stable oxidation state of Sg in aqueous solution is +6, and that like its homologs Mo and W, Sg forms neutral or anionic oxoor oxohalide-compounds under the present condition. In these first experiments, Sg exhibits properties very characteristic of group 6 elements, and does not show U-like properties.

Abstract: Seaborgium was previously eluted from cation exchange columns like its homologs molybdenum and tungsten in 0.1 Μ HNO3/5 Χ 10\" Μ HF. Its chemical form was presumably a neutral or anionic oxygen containing fluoride. However, species containing no fluoride such as SgOJ\" could not be excluded. In order to verify that fluoride complexing played a role in the previous study, another series of cation exchange separations was performed with 7-s Sg in which 0.1 Μ HN03 without HF was used as eluent. Sg and W were produced simultaneously by bombarding a Cm target containing Gd with 124 MeV Ne ions. While W was eluted from the cation exchange columns with an average chemical yield of 59%, no Sg decay chain was detected in the eluent even though about 5 aacorrelations were expected. This non-tungsten like behaviour of seaborgium is tentatively attributed to its lower tendency to hydrolyze compared to that of tungsten. In the previous experiments with seaborgium in the presence of fluoride ions, neutral or anionic fluoride complexes, e.g., Sg02F2 or SgC^Fä, were likely to be formed and were eluted from the cation exchange columns.