Hassium

Radioactive and Artificially Produced **What's in a name?** From the Latin word for the German state of Hessen, **Hassias**. **Say what?** Hassium is pronounced as **HAS-i-em**. **History and Uses:** Hassium was first produced by Peter Armbruster, Gottfried Münzenber and their team working at the [|Gesellschaft für Schwerionenforschung] in Darmstadt, Germany in 1984. They bombarded atoms of [|lead] -208 with ions of [|iron] -58 with a device known as a linear accelerator. This produced atoms of hassium-265, an [|isotope] with a [|half-life] of about 2 milliseconds (0.002 seconds), and a free [|neutron]. Hassium's most stable [|isotope], hassium-277, has a [|half-life] of about 12 minutes. It decays into [|seaborgium] -273 through [|alpha decay] or decays through spontaneous fission. Since only small amounts of hassium have ever been produced, it currently has no uses outside of basic scientific research.
 * Atomic Number:** 108
 * Atomic Weight:** 277
 * Melting Point:** Unknown
 * Boiling Point:** Unknown
 * Density:** Unknown
 * Phase at Room Temperature:** Solid
 * Element Classification:** Metal
 * Period Number:** 7 **Group Number:** 8 **Group Name:** none



Chemical investigation of hassium (element 108)
Ch. E. Düllmann [|1], [|2] , W. Brüchle [|3] , R. Dressler [|2] , K. Eberhardt [|4] , B. Eichler [|2] , R. Eichler [|2] , H. W. Gäggeler [|1] , [|2] , T. N. Ginter [|5] , F. Glaus [|2] , K. E. Gregorich [|5] , D. C. Hoffman [|5] , [|6] , E. Jäger [|3] , D. T. Jost [|2] , U. W. Kirbach [|5] , D. M. Lee [|5] , H. Nitsche [|5] , [|6] , J. B. Patin [|5] , [|6] , V. Pershina [|3] , D. Piguet [|2] , Z. Qin [|7] , M. Schädel [|3] , B. Schausten [|3] , E. Schimpf [|3] , H.-J. Schött [|3], S. Soverna [|1] , [|2] , R. Sudowe [|5] , P. Thörle [|4] , S. N. Timokhin [|8] , N. Trautmann [|4] , A. Türler [|9] , A. Vahle [|10] , G. Wirth [|3] , A. B. Yakushev [|8] & P. M. Zielinski [|5] Correspondence to: H. W. Gäggeler [|1], [|2] Correspondence and requests for materials should be addressed to H.W.G. (e-mail: Email: gaeggeler@iac.unibe.ch ). [|Topof page] 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 [|1,][|2,][|3,][|4]. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties [|5], whereas elements 106 and 107 both behave as expected from their position within the periodic table [|6,][|7]. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes 269Hs (refs [|8], [|9] ) and 270Hs (ref. [|10] ) in the fusion reaction between 26Mg and 248Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO4, 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 OsO4. 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.
 * 1) Departement für Chemie und Biochemie, Universität Bern, CH-3012 Bern, Switzerland
 * 2) Labor für Radio- und Umweltchemie, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
 * 3) Gesellschaft für Schwerionenforschung mbH, D-64291 Darmstadt, Germany
 * 4) Institut für Kernchemie, Universität Mainz, D-55128 Mainz, Germany
 * 5) Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
 * 6) Department of Chemistry, University of California, Berkeley, California 94720-1460, USA
 * 7) Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, P.R. China
 * 8) Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, 141980 Dubna, Russia
 * 9) Institut für Radiochemie, Technische Universität München, D-85748 Garching, Germany
 * 10) Research Center Rossendorf e.V., D-01314 Dresden, Germany

Oxidation states
Hassium is projected to be the fifth member of the 6d series of transition metals and the heaviest member of group VIII in the Periodic Table, below [|iron],[|ruthenium] and [|osmium]. The latter two members of the group readily portray their group oxidation state of +8 and this state becomes more stable as the group is descended. Thus hassium is expected to form a stable +8 state. Osmium also shows stable +5, +4 and +3 states with the +4 state the most stable. For ruthenium, the +6, +5 and +3 states are stable with the +3 state being the most stable. Hassium is therefore expected to also show other stable lower oxidation states.

Chemistry
The group VIII elements show a very distinctive [|oxide] chemistry which allows facile extrapolations to be made for hassium. All the lighter members have known or hypothetical tetroxides, MO4. The oxidising power decreases as one descends the group such that FeO4[|[30]] is not known due to an extraordinary [|electron affinity] which results in the formation of the well-known oxo-ion ferrate(VI), FeO42−. Ruthenium tetroxide, RuO4, formed by [|oxidation] of ruthenium(VI) in [|acid], readily undergoes [|reduction] to ruthenate(VI), RuO42−. Oxidation of ruthenium metal in air forms the dioxide, RuO2. In contrast, osmium burns to form the stable tetroxide, OsO4, which complexes with hydroxide ion to form an osmium(VIII) -ate complex, [OsO4(OH)2]2−. Therefore, eka-osmium properties for hassium should be demonstrated by the formation of a volatile tetroxide HsO4, which undergoes complexation with hydroxide to form a hassate(VIII), [HsO4(OH)2]2−.

Density
Hassium is predicted to have a bulk density of 41 g/cm3, the highest of any of the 118 known elements and nearly twice the density of [|osmium], the most dense measured element, at 22.6 g/cm3. This results from hassium's high atomic weight, the [|lanthanide and actinide contractions], and [|relativistic effects], although production of enough hassium to measure this quantity would be impractical, and the sample would quickly decay.[|[31]]

Gas phase chemistry
Hassium is expected to have the electron configuration [Rn]5f14 6d6 7s2 and thus behave as the heavier homolog of osmium (Os). As such, it should form a volatile tetroxide, HsO4, due to the tetrahedral shape of the molecule.

The first chemistry experiments were performed using gas thermochromatography in 2001, using 172Os as a reference. During the experiment, 5 hassium atoms were detected using the reaction 248Cm(26Mg,5n)269Hs. The resulting atoms were thermalized and oxidized in a He/O2 mixture to form the oxide.

269  108 Hs + 2 O2 → 269  108 HsO4 The measured deposition temperature indicated that hassium(VIII) oxide is less volatile than osmium tetroxide, OsO4, and places hassium firmly in group 8.[|[32]][|[33]]

<span style="font-family: Arial,Helvetica,sans-serif;">In order to further probe the chemistry of hassium, scientists decided to assess the reaction between hassium tetroxide and sodium hydroxide to form sodium hassate(VIII), a reaction well-known with osmium. In 2004, scientists announced that they had succeeded in carrying out the first acid-base reaction with a hassium compound