Tennessine is an artificially produced radioactive chemical element. It has the chemical symbol Ts and an atomic number (number of protons) of 117.
In 2010, Russian and American physicists and chemists working at the Joint Institute for Nuclear Research in Dubna, Russia, announced the creation of six atoms of tennessine, then simply called element 117. The atoms were created in two similar experiments that each ran continuously for more than 70 days. In 2015, the International Union of Pure and Applied Chemistry (IUPAC) assigned credit for the discovery of the element to the Dubna team and collaborating teams at the Lawrence Livermore National Laboratory in Livermore, California, and the Oak Ridge National Laboratory in Oak Ridge, Tennessee. IUPAC is the recognized authority in crediting the discovery of elements and assigning names to them.
Element 117 was officially named tennessine in 2016, to honor the contributions of the U.S. state of Tennessee to transactinide element research. In addition to Oak Ridge National Laboratory, two other Tennessee research institutions—the University of Tennessee-Knoxville and Vanderbilt University in Nashville—also helped discover tennessine.
Five of the six atoms created were atoms of the same isotope of tennessine. Isotopes are forms of an element with the same number of protons but different numbers of neutrons. The sixth atom represented a slightly heavier isotope. The isotopes had respective atomic mass numbers (total numbers of protons and neutrons) of 293 and 294. The scientists created the atoms in a device known as a particle accelerator. They used the accelerator to bombard a target made of the element berkelium (atomic number, 97) with calcium (atomic number, 20).
The researchers estimated that the half-life of isotope 293 is 0.014 second—that is, due to radioactive decay, only half the atoms in a sample of isotope 293 would still be atoms of that isotope after 0.014 second. The half-life of isotope 294 is approximately 0.078 second. To accurately determine half-life, scientists must study many atoms of an isotope. The small number of atoms of tennessine available only enabled scientists to estimate approximate values.
Chemists place tennessine in the transactinide group of transuranium elements. In the periodic table of the elements, tennessine is included in Group 17 (7A) with the halogens, a family of elements that includes chlorine and iodine. However, little is known about the properties of tennessine. Elements in the same family group have related properties because they have the same arrangement of electrons in their outermost or valence shell. Scientists can predict some of the properties of tennessine from its position in the periodic table. However, it is not possible to confirm some of these predictions without obtaining many more atoms of the element.
