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Science Innovation Centre · 113 · Nihonium

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Nihonium is a synthetic chemical element with symbol Nh and atomic number 113. It is extremely radioactive; its most stable known isotope, nihonium-286, has a half-life of about ten seconds. In the periodic table, nihonium is a p-block transactinide element. It is a member of the 7th period and is placed in group 13 on the periodic table, although it has not been confirmed to behave as the heavier homologue to thallium in that group.

Nihonium was first reported to have been created in 2003 by a Russian-American collaboration at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, and in 2004 by a team of Japanese scientists at RIKEN. The confirmation of their claims that took place in the ensuing years was an international endeavour, involving independent teams of scientists working in the United States, Germany, Sweden, and China as well as the original claimants working in Russia and Japan. In December 2015, the IUPAC-IUPAP Joint Working Party recognized the element and assigned the priority of the discovery and naming rights for the element to RIKEN, as it judged that the RIKEN team had persuasively demonstrated that their observations originated from element 113 while the JINR had not. The RIKEN team suggested the name nihonium in March 2016, which was approved and made official that November. The name comes from the common Japanese name for Japan.

Nihonium is expected to be within the “island of stability”, a concept which explains why some superheavy nuclides are anomalously long-lived, compared to the trend of rapidly decreasing stability after bismuth. Experiments support these theoretical predictions, with the half-lives of the confirmed nihonium isotopes increasing from milliseconds to seconds as neutrons are added and the island is approached. Nihonium is calculated to have some similar properties to its lighter homologues, boron, aluminium, gallium, indium, and thallium, and behave as a post-transition metal like the heavier four, although it should also show several major differences from them.