ununtrium

Ununtrium was the temporary systematic name assigned by IUPAC to the chemical element with atomic number 113. The name follows the convention for undiscovered or temporarily named elements, formed from the roots for one, one, and three (un-un-tri) with the standard suffix -ium, giving the symbol Uut. It is now obsolete as the element has been officially named nihonium (Nh).

The element was first synthesized in 2004 by a collaboration involving researchers at the Joint Institute for Nuclear Research in Dubna and Lawrence Livermore National Laboratory. It was produced in fusion-evaporation reactions that created very short-lived nuclei, which decayed within milliseconds to seconds. The experiments provided evidence for the existence of element 113, contributing to the mapping of the heaviest portion of the periodic table.

In 2016, IUPAC officially named the element nihonium, with the symbol Nh, in honor of Nihon, another name for Japan. The historic systematic name ununtrium is retained in historical references to describe the period before the official naming.

Predicted properties place nihonium in group 13 of the periodic table, as a heavy post-transition metal. It is expected to be highly unstable, with isotopes that decay rapidly via alpha emission. The anticipated electron configuration is [Rn] 5f14 6d10 7s2 7p1, and the chemistry is predicted to resemble other group 13 elements, exhibiting mainly +1 and +3 oxidation states. Given the short lifetimes of its isotopes, detailed chemical studies are limited.

Ununtrium, as a name, is of historical interest; contemporary references use nihonium. The element has no natural occurrence and has been produced only in minute quantities in particle accelerators for basic nuclear and chemical research.