Well, element 117, which has the titular name of “ununseptium”, was actually discovered by a team of Russians and Americans four years ago, and has been submitted for recognition as an “official element,” but its creation was just replicated by a group in Darmstadt, Germany, and that should speed its acceptance. The new discovery and its implications are described in a piece by Clara Moscowitz in Scientific American.
It’s amazing what physicists go through to make this stuff, but it had a fortuitious outcome:
To create 117, with the temporary periodic table placeholder name ununseptium, the researchers smashed calcium nuclei (with 20 protons apiece) into a target of berkelium (97 protons per atom). The experiment was so difficult in part because berkelium itself is tough to come by. “We had to team up with the only place on the planet where berkelium can be produced and isolated in significant quantities,” Düllmann says. That place is the Oak Ridge National Laboratory in Tennessee, which has a nuclear reactor that can create the rare element with a half-life of 330 days. It took the facility about two years to build up a large enough stock of berkelium for the experiment; when about 13 milligrams had accumulated, Oak Ridge scientists shipped it off to Germany for the next stage of the project. At GSI, researchers accelerated calcium ions to 10 percent light-speed and sent them colliding into the berkelium. If a calcium and berkelium nucleus collided head-on, occasionally the two nuclei would stick together, fusing to form a new element with a combined total of 117 protons. “We get about one atom per week,” Düllmann says.
One atom per week! It’s a triumph of our species that we can get one atom per week and then get enough of that stuff to identify it!
Now, as is usual for these trans-uranium elements, its half-life is very short: 0.05 seconds, but it’s identified by looking for the elements it forms upon decay: in this case (after several decays), lawrencium 266. That’s a new form of lawrencium (Lr, characterized by its 103 protons), for up to now the most common form of Lr was the 262 isotope, with 159 protons and half-life of 3.6 hours. Lawrencium-266, in contrast, has 163 protons and a half life of 11 hours. This has been seen as a confirmation of physicist’s predictions:
“Perhaps we are at the shore of the island of stability,” [Christoph] Düllmann says. [Düllmann led the German collaboration.]
No one knows for sure where this island lies, or even if it exists at all. Theory suggests that the next magic numbers beyond those known are around 108, 110 or 114 protons, and 184 neutrons. These configurations, according to calculations, could lead to special properties that allow atoms to survive much longer than similar species. “All existing data for elements 116, 117 and 118 do confirm that lifetimes increase as one goes closer to the neutron number 184, says theorist Witold Nazarewicz of Oak Ridge, who was not involved in the study. “This is encouraging.”
Well, I can’t say I understand the “island of stability” business at all (click the words in bold for more info), but perhaps one of our physics readers can explain that theory—if it’s not too arcane for general consumption.
Reporting from mid-book, Professor Ceiling Cat, Chicago.