This occurs in approximately 10 −16 seconds after the initial collision. To lose its excitation energy and reach a more stable state, a compound nucleus either fissions or ejects one or several neutrons, which carry away the energy. If fusion does occur, the temporary merger-termed a compound nucleus-is an excited state. Coming close alone is not enough for two nuclei to fuse: when two nuclei approach each other, they usually remain together for approximately 10 −20 seconds and then part ways (not necessarily in the same composition as before the reaction) rather than form a single nucleus. The strong interaction can overcome this repulsion but only within a very short distance from a nucleus beam nuclei are thus greatly accelerated in order to make such repulsion insignificant compared to the velocity of the beam nucleus. Two nuclei can fuse into one only if they approach each other closely enough normally, nuclei (all positively charged) repel each other due to electrostatic repulsion. The material made of the heavier nuclei is made into a target, which is then bombarded by the beam of lighter nuclei. The heaviest atomic nuclei are created in nuclear reactions that combine two other nuclei of unequal size into one roughly, the more unequal the two nuclei in terms of mass, the greater the possibility that the two react. Visualization of unsuccessful nuclear fusion, based on calculations by the Australian National University Thus far, reactions that created new elements were similar, with the only possible difference that several singular neutrons sometimes were released, or none at all.

Two nuclei fuse into one, emitting a neutron. See also: Superheavy element § Introduction A graphic depiction of a nuclear fusion reaction. A few key properties, such as its melting and boiling points and its first ionization energy, are nevertheless expected to follow the periodic trends of the halogens. As a result, tennessine is expected to be a volatile metal that neither forms anions nor achieves high oxidation states. Some of its properties may differ significantly from those of the lighter halogens due to relativistic effects. In the periodic table, tennessine is expected to be a member of group 17, the halogens. The synthesized tennessine atoms have lasted tens and hundreds of milliseconds. Tennessine may be located in the ' island of stability', a concept that explains why some superheavy elements are more stable compared to an overall trend of decreasing stability for elements beyond bismuth on the periodic table. In June 2016, the IUPAC published a declaration stating that the discoverers had suggested the name tennessine after Tennessee, United States, a name which was officially adopted in November 2016. In December 2015, the Joint Working Party of the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP), which evaluates claims of discovery of new elements, recognized the element and assigned the priority to the Russian–American team. The experiment itself was repeated successfully by the same collaboration in 2012 and by a joint German–American team in May 2014. One of its daughter isotopes was created directly in 2011, partially confirming the results of the experiment. The discovery of tennessine was officially announced in Dubna, Russia, by a Russian–American collaboration in April 2010, which makes it the most recently discovered element as of 2023.

It is the second-heaviest known element and the penultimate element of the 7th period of the periodic table. Tennessine is a synthetic chemical element with the symbol Ts and atomic number 117.

Oganesson element