Tennessine is the chemical element with the chemical symbol Ts and atomic number 117. Until 2016, it was known as Ununseptium, symbol Uus, from the Latin uni (1) and sept (7). It is not abundantly clear why the name was chosen; there was much discussion, the details of which would be laborious to evaluate. Tennessine was not observed until 2010, making it the last element to have been discovered.

Two isotopes, 294Ts and 293Ts have been observed. Tennessine is predicted to from isotopes ranging from the neutron dripline, somewhere in the vicinity of 415Ts down to 281Ts(1),(2),(3),(4). Of these, the most stable are predicted to occur in the band between 300Ts and 296Ts, with half-lives peaking at a few seconds. No isotope of Ts either has a long life or is the descendant of long-lived nuclides (types of atomic nuclei). If the distinction between "present" and "extinct" is taken to be a molar concentration [Ts] = 1.5E-30, relative to the sample on which it is a part, all isotopes of Ts have become extinct within 102.5 (316) sec. At that point local temperature will exceed 106 K, so Ts exists only(a) as positive ions with a minimum charge likely to be +8.

Tennessine has no chemistry. Properties such as its MP, BP, crystal structure, etc are meaningless.


1. "Decay Modes and a Limit of Existence of Nuclei"; H. Koura; 4th Int. Conf. on the Chemistry and Physics of Transactinide Elements; Sept. 2011.

2. “Systematic Study of Decay Properties of Heaviest Elements.”; Y. M. Palenzuelaa, L. F. Ruiza, A. Karpov, and W. Greiner; Bulletin of the Russian Academy of Sciences, Physics.  Vol . 76, No.11, pp 1165 – 1177; 2012

3. "Chart of the Nuclides, 2014", Japan Atomic Energy Agency; website available using "chart of nuclides" and "JAEA" as internet search terms.

4. "Nuclear Properties for Astrophysical Applications"; P. Moller & J. R. Nix; Los Alamos National Laboratory website; search by "LANL, T2", then "Nuclear Properties for Astrophysical Applications".


a. Except for one special case: a low-mass, population I (metal-rich) star, with a planet large enough to have an atmosphere and in an orbit which makes liquid water present in contact with both atmosphere and sunlight, several billion years to allow physicists and chemists to evolve, and a cultural willing-ness to spend vast sums of money to study Tennessine.