Nihonium – facts and properties

Position in the periodic table

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Occurrence and extraction

Nihonium can be found only where it is made. No stable isotope exists. For the longest-lived, nihonium-286, the literature quotes a half-life of a few seconds, but the value is uncertain. The isotope of the RIKEN experiments, nihonium-278, lasted only a fraction of a second.

The team around Kosuke Morita at the RIKEN Nishina Center fired zinc-70 ions at a bismuth-209 target. The principle was the same as at GSI, cold fusion, only with a different projectile. The yield was tiny. The detector recorded the first atom in 2004, the second in 2005 and the third not until 2012, after years of beam time. Its decay chain led through roentgenium, meitnerium and bohrium to isotopes that were already known, and that link made the proof convincing.

There was a question of priority. Groups from Dubna and Livermore had reported hints of nihonium isotopes as early as 2003, as decay products of moscovium. Their chains could not be connected to known nuclei, however. The joint working group of the societies IUPAC and IUPAP awarded the discovery to RIKEN at the end of 2015. The name nihonium was fixed in 2016. Nihon means Japan, literally something like "origin of the sun".

An older episode was the name nipponium. In 1908 the Japanese chemist Masataka Ogawa announced an element of that name, believing it to be the then undiscovered element below manganese. His measurements were later assigned to rhenium.

Properties and reactions

Nihonium is in period 7 and group 13, below thallium, with indium, gallium, aluminium and boron above. Predicted for nihonium is the electron configuration [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹. The atomic mass entry is 286 u, the mass number of nihonium-286. Nihonium has 3 valence electrons: two in the 7s and one in the 7p orbital.

There is no sample, and neither melting point nor boiling point nor density has been measured. Calculations predict a metal that is solid at room temperature, with a melting point of several hundred degrees Celsius and a density above that of thallium. Whether nihonium is a typical metal remains open.

The chemistry is the interesting part of the prediction. Further down the group the oxidation state plus one becomes more important, and in thallium it is the most common. In nihonium a relativistic effect adds to this: the single outer p electron drops in energy and is bound more firmly. Calculations therefore predict that plus one is favoured even more strongly than in thallium and that plus three plays hardly any role. That would break the pattern of the lighter elements in its group. First experiments with single atoms, most recently at GSI in 2024, suggest that nihonium is less reactive than thallium, but the number of atoms is small.

Thallium and its salts are very poisonous. Nihonium, by contrast, poses no danger because of the tiny quantities.

Research and synthesis

Nihonium is studied in basic research only. After three atoms in eight years it is clear how laborious it would be to make more.

The detection method is a lesson in how superheavy elements are handled. The detector does not say which element arrived. It supplies the place and time of each decay. Researchers assemble the chain from these and check whether its last link is a known nucleus. Only that connection turns an event into a discovery. RIKEN's first two chains ended in fission, which was not enough.

For theory, nihonium is a case in which calculations on relativity in p electrons can be tested, much as gold does for d electrons. Further experiments must show whether the calculations hold in detail. There are no applications.

Quick question

What is the atomic number of nihonium (Nh)?

FAQ