Ununhexium Traditional Geocache

Ununhexium is the temporary name of a synthetic superheavy element with the temporary symbol Uuh and atomic number 116. It is placed as the heaviest member of group 16 (VIA) although a sufficiently stable isotope is not known at this time to allow chemical experiments to confirm its position as the heavier homologue to polonium. It was first detected in 2000 and since the discovery about 30 atoms of ununhexium have been produced, either directly or as a decay product of ununoctium, and are associated with decays from the four neighbouring isotopes with masses 290–293. The most stable isotope to date is Uuh-293 with a half-life of ~60 ms.

On July 19, 2000, scientists at Dubna (JINR) detected a single decay from an atom of ununhexium following the irradiation of a Cm-248 target with Ca-48 ions. The results were published in December, 2000. This 10.54 MeV alpha-emitting activity was originally assigned to ²⁹²Uuh due to the correlation of the daughter to previously assigned ²⁸⁸Uuq. However, that assignment was later altered to ²⁸⁹Uuq, and hence this activity was correspondingly changed to ²⁹³Uuh. Two further atoms were reported by the institute during their second experiment between April–May 2001.

In the same experiment they also detected a decay chain which corresponded to the first observed decay of ununquadium and assigned to ²⁸⁹Uuq. This activity has not been observed again in a repeat of the same reaction. However, its detection in this series of experiments indicates the possibility of the decay of an isomer of ununhexium, namely ^293bUuh, or a rare decay branch of the already discovered isomer,^293aUuh, in which the first alpha particle was missed. Further research is required to positively assign this activity. The team repeated the experiment in April–May 2005 and detected 8 atoms of ununhexium. The measured decay data confirmed the assignment of the discovery isotope as ²⁹³Uuh. In this run, the team also observed ²⁹²Uuh in the 4n channel for the first time. In May 2009, the Joint Working Party reported on the discovery of copernicium and acknowledged the discovery of the isotope ²⁸³Cn. This implies the de facto discovery of ununhexium, as ²⁹¹Uuh, from the acknowledgment of the data relating to the granddaughter ²⁸³Cn, although the actual discovery experiment may be determined as that above. An impending JWP report will discuss these issues further.

Ununhexium (Uuh) is a temporary IUPAC systematic element name. Research scientists usually refer to the element simply as element 116 (or E116). According to IUPAC recommendations, the discoverer(s) of a new element has the right to suggest a name. The JWP has not yet officially accepted the discovery of element 116 and so the naming process has not yet begun.