Darmstadtium – facts and properties

Position in the periodic table

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Occurrence and extraction

Darmstadtium is absent from nature. The isotope of the discovery, darmstadtium-269, lasted only a fraction of a millisecond. For the longest-lived, darmstadtium-281, the literature quotes half-lives from a few seconds up to about a quarter of a minute. Few decays have been observed, so these values are uncertain.

In the autumn of 1994 a team at GSI, including Sigurd Hofmann, Fritz Peter Heßberger, Peter Armbruster and Gottfried Münzenberg, bombarded a layer of lead-208 with nickel-62 ions. As with meitnerium, the process was cold fusion, in which the merged nuclei carry little excitation energy. The detector registered one atom whose alpha decays led through hassium-265 and seaborgium-261 to known nuclei. That is how the new nucleus was recognised. Later experiments, some outside Darmstadt, confirmed the discovery.

Like dubnium and berkelium, the name recalls a place rather than a person. Darmstadt is the seat of GSI, which has worked there with heavy ions for decades. The same research also gave rise to a method of cancer therapy with carbon ions. Darmstadtium was officially confirmed as an element name in 2003.

Properties and reactions

Darmstadtium is in period 7 and group 10, below platinum, with palladium and nickel above. The electron configuration [Rn] 5f¹⁴ 6d⁸ 7s² comes from calculations. The atomic mass 281 u stands for the mass number of darmstadtium-281, not the average of a natural mixture.

Almost nothing about darmstadtium has been measured. Every figure for melting point, boiling point and density comes from calculations, or is missing. The calculations point to a solid, extremely dense metal whose density might exceed twenty-five grams per cubic centimetre, clearly more than platinum. That, too, is a calculated result and not a measurement.

The chemical expectation follows platinum: darmstadtium should be a very noble, barely reactive metal that resists acids. Following platinum, the oxidation states plus two, plus four and plus six come into question. Nobody knows whether that holds, because no chemical experiment with darmstadtium has been carried out. One atom per run, a lifetime of seconds and a production that takes days set narrow limits.

Decay proceeds by alpha emission or spontaneous fission, and the tiny amounts involved pose no danger.

Research and synthesis

Darmstadtium is studied only in basic research. The central question is how nuclei are built at the edge of the periodic table. The first atoms were neutron-poor, and their nuclei lie far below the neutron number at which theory expects special stability. Later, heavier darmstadtium isotopes turned up as intermediate steps in the decay chains of still larger elements made by hot fusion in Dubna. Comparing the half-lives shows how strongly extra neutrons stabilise the nucleus.

Production is a game of patience. The probability that a projectile and a target nucleus really fuse is tiny. Days or weeks of irradiation yield a single atom. None of this can be put to use: there is no application, and any amount one could weigh stays theory.

For theory, darmstadtium is an interesting test case. The comparison with platinum shows how strongly relativity alters the electrons of heavy atoms. If a chemical experiment ever succeeds, it would be the first check of whether the calculations are right to expect a noble metal.

Quick question

What is the atomic number of darmstadtium (Ds)?

FAQ