19: Two New Elements Discovered

By Elizabeth SvobodaJan 3, 2005 6:00 AM


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In February the world was treated to a transcontinental eureka moment: Scientists from the Lawrence Livermore National Laboratory in California and the Joint Institute for Nuclear Research in Russia announced they had discovered two new chemical elements. Called superheavies because of their large atomic mass, elements 113 and 115 lasted little more than a second. Their brief existence, however, lends credence to the theory that an island of stable heavy elements with unique chemical properties exists within the undiscovered reaches of the periodic table.

The elements were born in a high-powered circular particle accelerator in Dubna, Russia. After chemists at Livermore produced a rare isotope of the element americium, they shipped it to their Russian colleagues, who beamed calcium ions at it with the accelerator. “Every once in a rare while, a calcium ion fused with an americium nucleus, and we got an element 115 isotope,” says nuclear chemist Ken Moody, who led the Livermore team. Since each calcium nucleus contains 20 protons and each americium nucleus has 95, he was pleased, but not surprised, that an element of 115 protons resulted. But it had a littermate—an element with 113 protons that appeared after element 115 underwent radioactive decay.

The new elements, tentatively dubbed ununtrium (113) and ununpentium (115), will have to be independently re-created before they are written into the periodic table. Moody and his team are already looking to build on their results by using other neutron-rich elements to create new stable elements with unpredictable properties. (In general, the more neutrons in an element, the more stable it will be.) Moody hopes the discovery of stable superheavy elements will help scientists better understand the mechanics of how nuclei are held together, opening the door for future discoveries in nuclear power generation or weapons development. “We’re at the edge of the island of stability, where the half-lives of the new elements are relatively long,” Moody says. “Now we just have to find a projectile and target with the highest number of neutrons possible.”

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