Darmstadtium


 * Name: Darmstadtium
 * Symbol: Ds
 * Atomic number: 110
 * Atomic Weight: 281
 * Standard State: presumably a solid at 298 K [[image:Darmstadtium.jpg width="152" height="147"]]
 * Group: 10
 * Group Name: (none)
 * Period: 7
 * Color: unknown, but probably metallic and silvery white or grey in appearance
 * Classification: Metallic

__**Brief description:**__ Element 110, darmstadtium, is a synthetic element that is not present in the environment at all. Further information on element 110 is [|here] (outside WebElements) and in a [|press release] (outside WebElements). The interested reader should consult the on-line version of [|The Wonderful World of Atoms and Nuclei] for a fascinating insight into research on "super-heavy" atoms. Chemically, darmstadtium is in the same Group as nickel, palladium, and platinum (Group 10). Unlike these lighter atoms, darmstadtium decays after a small fraction of a thousandth of a second into lighter elements by emitting α-particles which are the nuclei of helium atoms.

[|Isolation]: only a few atoms of darmstadtium have ever been made, initially through a nuclear reaction involving fusion of an isotope of lead, Pb, with one of nickel, Ni. 208Pb + 62Ni → 269Ds + 1n Isolation of an observable quantity has never been achieved, and may well never be. This is because atoms of the element decompose through the emission of α-particles with a half life of only about 270 microseconds. Another isotope was made by using a different isotope of nickel. 208Pb + 64Ni → 271Ds + 1n

The direct production of 270Ds has clearly identified two alpha groups belonging to two isomeric levels. The ground state decays into the ground state of 266Hs by emitting an 11.03 MeV alpha particle with a half-life of 0.10 ms. The isomeric level decays by alpha emission with alpha lines at 12.15,11.15 and 10.95 MeV with a half-life of 6 ms. The 12.15 MeV has been assigned as decay into the ground state of 266Hs indicating that this high spin K-isomer lies at 1.12 MeV above the ground state.

Discovery of Darmstadtium
Darmstadtium was first synthesized by research scientists at the Heavy Ion Research Laboratory in Darmstadt, Germany in 1994. The element was made by bombarding lead-208 atoms with nickel-62 atoms in a heavy ion accelerator. Four atoms of darmstadtium were produced in the first experiment. The element is named after the city where it was first made. In addition to darmstadtium, the Heavy Ion Research Laboratory has been responsible for the discovery of several heavy elements: bohrium in 1981, meitnerium in 1982, hassium in 1984, roentgenium in 1994, and copernicium in 1996.


 * Darmstadtium** is a [|chemical element] with the symbol **Ds** and [|atomic number] 110. It is placed as the heaviest member of group 10, but no known isotope is sufficiently stable to allow chemical experiments to confirm its placing in that group as a heavier [|homologue] to [|platinum]. This [|synthetic element] is one of the so-called [|super-heavy atoms] and was first synthesized in 1994, at a facility near the city of [|Darmstadt], Germany, from which it takes its name. The longest-lived and heaviest isotope known is 281aDs with a [|half-life] of ~10 s although a possible [|nuclear isomer], 281bDs has an unconfirmed [|half-life] of about 4 minutes.

Hot fusion
//This section deals with the synthesis of nuclei of darmstadtium by so-called "hot" fusion reactions. These are processes which create compound nuclei at high excitation energy (~40-50 MeV, hence "hot"), leading to a reduced probability of survival from fission. The excited nucleus then decays to the ground state via the emission of 3-5 neutrons. Fusion reactions utilizing 48Ca nuclei usually produce compound nuclei with intermediate excitation energies (~30-35 MeV) and are sometimes referred to as "warm" fusion reactions. This leads, in part, to relatively high yields from these reactions.// 232Th(48Ca,xn)280-xDs The synthesis of darmstadtium by hot fusion pathways was first attempted in 1986 by the team at Dubna. Using the method of detection of [|spontaneous fission], they were unable to measure any SF activities and calculated a cross section limit of 1 pb for the decay mode. In three separate experiments between November 1997 and October 1998, the same team re-studied this reaction as part of their new 48Ca program on the synthesis of superheavy elements. Several SF activities with relatively long half-lives were detected and tentatively assigned to decay of the daughters 269Sg or 265Rf, with a cross section of 5 pb. These observations have not been confirmed and the results are taken as only an indication for the synthesis of darmstadtium in this reaction. 232Th(44Ca,xn)276-xDs This reaction was attempted in 1986 and 1987 by the Dubna team. In both experiments, a 10 ms SF activities was measured and assigned to 272Ds, with a calculated cross section of 10 pb. This activity is currently not thought to be due to a darmstadtium isotope. 238U(40Ar,xn)278-xDs This reaction was first attempted by the Dubna team in 1987. Only spontaneous fission from the transfer products 240mfAm and 242mfAm were observed and the team calculated a cross section limit of 1.6 pb. The team at GSI first studied this reaction in 1990. Once again, no atoms of darmstadtium could be detected. In August 2001, the GSI repeated reaction, without success, and calculated a cross section limit of 1.0 pb. 236U(40Ar,xn)276-xDs This reaction was first attempted by the Dubna team in 1987. No spontaneous fission was observed. 235U(40Ar,xn)275-xDs This reaction was first attempted by the Dubna team in 1987. No spontaneous fission was observed. It was further studied in 1990 by the GSI team. Once again, no atoms were detected and a cross section limit of 21 pb was calculated. 233U(40Ar,xn)273-xDs This reaction was first studied in 1990 by the GSI team. No atoms were detected and a cross section limit of 21 pb was calculated. 244Pu(34S,xn)278-xDs (x=5) In September 1994 the team at Dubna detected a single atom of 273Ds, formed in the 5n neutron evaporation channel. The measured cross section was just 400 femtobarns (fb).

**Oxidation states **
Darmstadtium is projected to be the eighth member of the 6d series of transition metals and the heaviest member of group 10 in the Periodic Table, below [|nickel], [|palladium] and [|platinum]. The highest confirmed oxidation state of +6 is shown by platinum whilst the +4 state is stable for both elements. Both elements also possess a stable +2 state. Darmstadtium is therefore predicted to show oxidation states +6, +4, and +2.

**Chemistry **
High oxidation states are expected to become more stable as the group is descended, so darmstadtium is expected to form a stable hexafluoride, DsF6, in addition to DsF5 and DsF4. Halogenation should result in the formation of the tetrahalides, DsCl4, DsBr4, and DsI4.

Like other Group 10 elements, darmstadtium can be expected to have notable hardness and catalytic properties.