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Four elements earn permanent seats on the periodic table

U.S., Russian and Japanese scientists credited with official discoveries

4:58pm, December 31, 2015

FEWER U’S  The official discovery of elements 113, 115, 117 and 118 means that all 118 elements in the periodic table’s first seven rows have been found on Earth or produced in the lab.  The four new elements will soon get names replacing the temporary “Uu” placeholder names.

The seventh row of the periodic table is officially full.

On December 30, the International Union of Pure and Applied Chemistry announced that a Russian-U.S. collaboration had attained sufficient evidence to claim the discovery of elements 115, 117 and 118.  IUPAC awarded credit for the discovery of element 113 to scientists at RIKEN in Wako, Japan (SN Online: 9/27/12).  Both groups synthesized the elements by slamming lighter nuclei into each other and tracking the decay of the radioactive superheavy elements that followed.

Researchers at the Joint Institute for Nuclear Research in Dubna, Russia, and Lawrence Livermore National Laboratory in California, which are among the institutions credited with elements 115, 117 and 118, had also laid claim to element 113 after experiments in 2004 (SN: 2/7/04, p. 84) and 2007.  But garnering recognition for the three other elements softened the blow, says Dawn Shaughnessy, who leads the experimental nuclear and radiochemistry group at Livermore.  “I’m personally very happy with IUPAC’s decision,” she says.

Published reports on the newly recognized elements will appear in early 2016, says IUPAC executive director Lynn Soby.  Official recognition of the elements means that their discoverers earn the right to suggest names and symbols.  Element 113 will be the first element discovered and named by researchers in Asia.

Editor’s note:  This article was updated on Jan. 1, 2016, to correct the abbreviation of strontium in the image of the periodic table.