Magazine article Science News

A Chemical Glance at Short-Lived Elements

Magazine article Science News

A Chemical Glance at Short-Lived Elements

Article excerpt

A chemical glance at short-lived elements

The chemical elements lawrencium, rutherfordium and hahnium hardly contribute to the stuff of everyday life. Synthesized one atom at a time by bombarding heavy nuclei with ions, these highly radioactive elements generally survive just a few seconds before decaying into other atomic isotopes.

Darleane C. Hoffman of the Lawrence Berkeley (Calif.) Laboratory and her co-workers, including collaborators in West Germany and Switzerland, have taken up the challenge of determining the chemical properties of these short-lived elements. Such studies enable researchers to see where the elements fit into the periodic table and whether they follow the trends in chemical behavior evident among lighter elements along the table's rows and columns. The researchers also look for evidence of new isotopes, in which the number of neutrons present in a nucleus differs from known varieties, and for traces of spontaneous fission, in which a newly synthesized nucleus immediately splits into two pieces.

Hoffman's team has been focusing on hahnium, or element 105. From its assigned position in the periodic table, hahnium ought to behave like its stable neighbor tantalum. However, recent experiments show that hahnium has a number of chemical properties resembling those of protactinium, a naturally occuring element situated beside uranium in the so-called actinide series. Protactinium is a dangerous, highly toxic material that requires precautions similar to those used when handling plutonium.

"Like plutonium, hahnium seems to have very nasty properties," Hoffman says. "There are many challenges in these studies of the heaviest elements." She described the results of her team's investigations at last week's American Chemical Society meeting in Washington, D.C.

The researchers synthesize hahnium by firing oxygen ions into a target consisting of berkelium-249. The resulting isotope, hahnium-262, has a half-life of 35 seconds, allowing only a tantalizingly brief interval in which to dissolve the isotope in water to study its chemistry in solution, or to react it with bromine to study its properties as a gas. …

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