- Nihonium (Nh) is a synthetic, radioactive element with atomic number 113, belonging to Group 13 of the periodic table, directly beneath thallium. It is part of the transactinide series and the 7p block of elements.
- Its predicted electron configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹, consistent with other Group 13 elements such as boron, aluminum, gallium, indium, and thallium. Nihonium is expected to exhibit a +1 oxidation state as its most stable form, with +3 possible but less stable due to relativistic effects that strongly stabilize the 7s² “inert pair.” The atom contains one hundred and thirteen protons, about one hundred and seventy to one hundred and seventy-eight neutrons depending on the isotope, and one hundred and thirteen electrons arranged in seven shells.
- The most stable known isotope is nihonium-286 (²⁸⁶Nh), with a half-life of about 20 seconds, while other isotopes typically last less than a second.
- Nihonium was first synthesized on July 23, 2003, at the RIKEN Nishina Center for Accelerator-Based Science in Wako, Japan, by a team led by Kosuke Morita. The discovery was achieved by bombarding a bismuth-209 (²⁰⁹Bi) target with accelerated zinc-70 (⁷⁰Zn) ions, producing a single atom of nihonium-278 (²⁷⁸Nh). Later experiments in 2004 and 2005 produced more atoms, confirming the discovery. This marked the first time that a superheavy element had been discovered in Japan, making Nihonium the first element named after an Asian country.
- The name nihonium comes from Nihon (日本), one of the Japanese words for “Japan,” and means “the Land of the Rising Sun.” The symbol Nh was officially approved by IUPAC in 2016, alongside the naming of moscovium, tennessine, and oganesson.
- Due to its extremely short half-life and production atom by atom, nihonium has no practical applications. Its importance lies in extending the periodic table, verifying nuclear models, and testing relativistic effects in heavy p-block elements.
- Chemically, nihonium is predicted to behave like thallium, favoring the +1 oxidation state because of the inert pair effect. It may form simple compounds such as nihonium(I) chloride (NhCl) and nihonium(I) hydroxide (NhOH). However, relativistic effects may make nihonium more metallic or chemically inert than expected. Because so few atoms have ever been produced, experimental chemical data are not yet available.
- Biologically, nihonium has no role and would be radiotoxic if it were available in macroscopic amounts. However, its short half-life ensures it poses no practical biological risk.
- Environmentally, nihonium does not exist in nature and must be created artificially in particle accelerators. It decays rapidly into lighter elements, leaving no environmental impact.
