BERKELIUM

AMANDA YARNELL, C&EN WASHINGTON

BERKELIUM AT A GLANCE
Name: Named after Berkeley, California, its place of discovery.
Atomic mass: (247).
History: First produced in 1949 by Stanley G. Thompson, Albert Ghiorso, and Glenn T. Seaborg.
Occurrence: Does not occur naturally. Can be made artificially by bombarding Am-241 with -particles.
Appearance: Silvery, solid metal.
Behavior: Highly radioactive.
Uses: Pure berkelium has not yet been isolated, and of the compounds formed, only one has been created in a visible amount--three-billionths of a gram of berkelium chloride. Because it only exists in such small quantities, berkelium has no commercial uses.
Although it may not be the city's most obvious point of civic pride, Berkeley, Calif., has something no other city in the United States does: a spot on the periodic table.

It gained this distinction in December 1949, when chemists at the University of California, Berkeley, managed to extend the periodic table once again, to element 97. UC Berkeley scientists, including Chemistry Nobel Prize winners Edwin M. McMillan and Glenn T. Seaborg, had already created four new elements beyond uranium. The quest to synthesize a fifth was undertaken by Seaborg and his longtime collaborators Albert Ghiorso and Stanley G. Thompson in 1946.

With four transuranium elements under their belts, the road to element 97 seemed fairly straightforward. But a number of hurdles--producing sufficient quantities of the required americium starting material, establishing ways of handling this highly radioactive material, and developing extremely efficient methods of separating the elements produced--slowed their progress. After three years of trying, the team used a-particles generated in the university's cyclotron to bombard several milligrams of americium-241 produced by prolonged neutron bombardment of plutonium. Seven hours and several ion-exchange columns later, they managed to isolate a detectable quantity of element 97. The first isotope they produced of the new element had a mass of 243 and a half-life of nearly four-and-a-half hours.

Then came the matter of a name. In fact, Seaborg noted at a 1975 symposium commemorating the 25th anniversary of element 97's discovery that "a name had been chosen even before it was discovered." They promptly christened it "berkelium."

As prophesied by Danish chemist Niels Bohr, element 97 behaved similarly to its upstairs neighbor on the periodic chart, terbium. Terbium is one of no less than four elements named after Ytterby, a Swedish village so small that it doesn't even merit an appearance in my world atlas.

The village of Ytterby's claim to chemical fame is a nearby feldspar quarry. It was from this quarry that a Finnish chemist named Johan Gadolin first turned up the curious black rock from which many of the rare-earth elements were eventually isolated. Ytterby's mineral riches eventually earned it the rare distinction of being immortalized in the names of four elements: yttrium (element 39), terbium (element 65), erbium (element 68), and ytterbium (element 70).

EXTRA! EXTRA! The announcement of the discovery of yet another new element by UC Berkeley scientists made newspaper headlines.
COURTESY OF LAWRENCE O. BERKELEY NATIONAL LABORATORY
By analogy to its chemical homolog terbium, berkelium was named after its birthplace. Beyond their places on the periodic table, however, the city of Berkeley bears little resemblance to the village of Ytterby.

For one, Berkeley is populous enough to make it into my atlas. What's more, it's known for far more than just its place on the periodic table. For Americans, the city conjures up memories of the cultural and political turbulence of the 1960s. And for chemists, the city brings to mind UC Berkeley, long an epicenter of chemical research.

The Berkeley team's periodic table tributes to their city, state, and country--between 1944 and 1950, UC Berkeley scientists had reported the discovery of berkelium, californium (element 98), and americium (element 95)--briefly caught the attention of some members of the U.S. media. At the same 1975 symposium, Seaborg recounted the musings of a reporter for the Des Moines Register who wondered what Seaborg and his team would name an element if it had been found in, say, Vinegar Bend, Ala., or Pysht, Wash.

Apparently this reporter hadn't heard a name like Ytterby had inspired not just one but four element names.

In fact, alabamine almost did make the periodic table. In the 1930s, chemists at the Alabama Polytechnic Institute (now Auburn University) thought they had discovered elements 85 and 87, christening them alabamine and virginium. And several years earlier, in the 1920s, chemists at the University of Illinois claimed to have discovered element 61, dubbing it illinium. Each of these discoveries turned out to be a false alarm, however, leaving Berkeley as the only American city and California as the only American state honored in the periodic table.

This particular honor doesn't carry the same weight with everyone, though. At the symposium, Seaborg expressed regret that not everyone shared his own excitement about the name given to element 97. "I remember calling the mayor of Berkeley with the glad tidings and being very disappointed at his complete lack of interest," he lamented.

I wonder how the mayor of Ytterby felt.


Amanda Yarnell is an associate editor at Chemical & Engineering News. She covers enzymology and topics at the interface of chemistry and biology for C&EN's Science, Technology & Education department.

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