NEWS OF THE WEEK
PROBING ELEMENT 112'S CHEMISTRY Just two atoms of element 112 were enough for Eichler (left) and Rugard Dressier of the Paul Scherrer Institute to probe the transactinide's chemical properties.
TRANSACTINIDES: The superheavy element behaves like mercury
O
N THE BASIS OF a nuclear synthesis experiment that yielded just two atoms of element 112, scientists have determined that the super heavyweight's chemical properties are similar to those of mercury, the element directly above it in the periodic table. Predicting electron orbital structures of transactinides is challenging because of so-called relativistic effects. That term refers to the energy-altering influence of the large concentration of positive charge in the nuclei of the heaviest elements on the electrons orbiting those nuclei. Those forces can alter the configuration of an atom's valence orbitals—and hence its chemical properties—compared with the electronic structure expected solely on the basis of an element's position in the periodic table. In the case of element 112, the transactinide's atomic number places it in group 12 together with zinc, cadmium, and mercury. Earlier theoretical work suggests that
112 should indeed exhibit chemical behavior typical of group 12 elements. Other calculations, however, predict that 112 will behave like radon, a noble gas in group 18. Now, a team of 25 researchers from Switzerland, Russia, and Poland reports that an experimental study that directly compared element 112's volatility and adsorption characteristics with those of mercury and radon indicates that the transactinide behaves like its lighter group-12 homolog, mercury (Nature 2007,447> 72)By firing a beam of48Ca projectiles at a ^ P u target that was doped with Nd203, Robert Eichler of the Paul Scherrer Institute, Villigen, Switzerland, and coworkers from the Joint Institute for Nuclear Research, Dubna, Russia, and elsewhere produced two atoms of element 112, as well as various radioactive mercury and radon nuclei. The products were then swept in a gas stream to a series of temperature-controlled gold-covered detectors. The group observed that similar to mercury (and in contrast to radon), element 112 is mildly volatile and bonds readily to gold. With only two atoms of the transactinide to look at, it remains unclear if the element can also take on mercury's signature liquid form. The team notes that the relatively long lifetimes of the two atoms (several seconds as opposed to a fraction of a second) add to the growing experimental evidence for the existence of the island of stability, a region on the chart of nuclides in which certain superheavy nuclei are predicted to be especially stable.—MITCH JACOBY
SCRIBBLING ON IONIC LIQUIDS
beam passes over and interacts with the solid sample surface, lines of positive charges are created. These written patterns can be erased by warming the sample until it liquefies or by flooding the surface with low-energy electrons to neutralize the surface charges, Licence explains. MATERIALS SCIENCE: Etching The micrometer resolution of the patterns is "only patterns on the frozen surface of just a start," Licence notes, and is merely a circumorganic salts suggests applications stance of the instrument his group has been using. In planned experiments using a focused ion beam, pattern resolution down to 10 nm should be possible, he says. APITALIZING ON a chance discovery, chemists And the low temperature of the current experiments should not be a detriment, he adds, because an ionic Inside a vacuum at the University of Nottingham, in England, chamber, ion beams liquid with a melting point at or above room temperafound that they could write and erase patterns can etch patterns on on the surface of a frozen ionic liquid (Angew. Chern. Int. ture could be used. In that case, the surface could be frozen ionic liquid patterned at room temperature and erased by slight Ed., DOI: io.ioo2/anie.200700i44). samples. Peter Licence and coworkers Frank J. M. Rutten and warming or by washing with low-energy electrons. Haregewine Tadesse believe the method could one day The ionic liquid write-erase phenomenon "is fasbe applied to data storage, photolithography, and cinating," says Kenneth R. Seddon, an ionic liquids a variety of other materials applications. expert at Queen's University Belfast, in Northern Ireland. Ionic liquids function as catalysts, solvents, and The chemists were studying thin layers of solid -NQN*- *ChL materials for an increasing number of applications that i-ethyl-3-methylimidazolium ethylsulfate at its are beginning to be commercialized, Seddon notes. But melting point (-85 °C) by time-of-flight secondthis work is the first application that takes advantage of ary-ion mass spectrometry as part of their ultrahigh-vacuum research on ionic liquids. That's how the surface chemistry of an ionic liquid, he says. they figured out that the gallium ion beam source The Nottingham research is "a great example of the of the spectrometer could be used to etch patterns untapped potential for ionic liquids as tunable mulinto the surface of frozen samples. tipurpose materials," adds Robin D. Rogers, an ionic l-Ethyl-3-methylJmid When they solidify, ionic liquids lose their conliquids specialist at the University of Alabama, Tuscaazolium ethylsulfate ductivity and become insulators. But as the ion loosa.—STEVE RITTER
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MAY 7, 2007
