The Convoluted Story Of How The First Atoms Of Tennessine Were Created
AILSA CHANG, HOST:
There are rare chemical elements, and then there is tennessine. Only a couple dozen atoms of the stuff have ever existed. For the 150th anniversary of the periodic table, NPR science correspondent Joe Palca has the convoluted story of one of the latest elements to be added.
JOE PALCA, BYLINE: Tennessine lies at the outer edges of the periodic table. It's one of a group of unstable synthetic elements that don't last very long before they vanish. To make tennessine, you need to fuse together two existing elements - in this case, calcium and another nonnatural element, berkelium. And the only place you can get enough berkelium to try to do that is a special nuclear reactor at the Department of Energy Oak Ridge National Laboratory in Tennessee. What comes out of the reactor is a mixture of exotic elements. The berkelium has to be separated out.
CLARICE PHELPS: They perform that separation, and they give us what's called the Berkelium cut.
PALCA: Clarice Phelps is a researcher at Oak Ridge. She and her colleagues then purified the berkelium.
PHELPS: It took us a couple of months, about three months.
PALCA: Finally, they had about 22 milligrams of the pure stuff. Now, there are only a handful of labs that can fire calcium ions at a berkelium target to make tennessine. One is in Russia. So Oak Ridge packed up the highly radioactive berkelium in specially shielded containers. A shipping company sent the containers up to New York's JFK Airport. There, they were loaded onto a plane headed for Moscow. But there was a problem.
KRZYSZTOF RYKACZEWSKI: Somebody in this, you know, shipping company forgot to give papers to the captain (ph).
PALCA: Krzysztof Rykaczewski is a senior researcher at Oak Ridge. He says when the plane landed, Russian customs agents were confronted with several large containers festooned with hazardous material labels and no paperwork describing the contents.
RYKACZEWSKI: They immediately sent it back with the same plane to New York.
PALCA: After returning to JFK, the berkelium set off again, with shipping papers. According to Rykaczewski, this time the customs agents said, yes, the papers are in order.
RYKACZEWSKI: But we would like to have such papers by fax when the plane is starting so we are better prepared to receive the cargo.
PALCA: Back to New York again. On the fifth trans-Atlantic flight, the berkelium was allowed into Russia, where it was sent on yet another plane to the Joint Institute of Nuclear Research in Dubna. For five months, scientists there used the cyclotron to fire calcium ions at the berkelium, hoping some of them would fuse with the target to form Element 117, what would later be called tennessine. Rykaczewski says the expectation was they wouldn't see the element directly; it was likely only to last a fraction of a second. Instead, they expected to see a specific pattern as 117 decayed into lighter elements.
RYKACZEWSKI: And everything was nicely fitting to the picture that we observed - six decays of Element 117.
PALCA: In other words, in five months, they only got six atoms of tennessine. When I first heard that name, I thought it was a mistake. All the other synthetic elements ended in -ium - think plutonium or americium. Oak Ridge nuclear engineer Julie Ezold understands my confusion.
JULIE EZOLD: We all thought it was going to be that way as well. But remember - the periodic table has rules.
PALCA: Ezold says Element 117 fits in a column of the periodic table filled with compounds called halogens - fluorine, chlorine, bromine.
EZOLD: Therefore, its name had to end in -ine. So instead of tennessium (ph), it's tennessine.
PALCA: Tennessine might not be the last element to be added to the periodic table. The search is underway for new ones. I asked Krzysztof Rykaczewski if he was part of the search.
RYKACZEWSKI: Yes. It's fun, you know? It's a really great thing to discover a new element (laughter).
PALCA: Joe Palca, NPR News.
(SOUNDBITE OF VAGABON'S "MAL A L'AISE")
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