![Tennessine element card: symbol Ts, atomic number 117, atomic mass [294], electron configuration [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵, Unknown, group 17, period 7.](https://stage.chemistry-dictionary.com/wp-content/uploads/2026/09/tennessine-chemical-element.webp)
Tennessine sits in group 17 and period 7 of the periodic table. This spot makes it the heaviest known member of the halogen family. It sits right below lighter halogens like iodine and astatine.
However, its huge size causes strange physics changes called relativistic effects. These effects happen in superheavy atoms and change how their electrons move. Because of this, tennessine will likely act more like a metal.
It probably will not act like typical nonmetal halogens such as fluorine or chlorine. Advanced computer models suggest the element favors a +1 or +3 oxidation state. This state tells us how many electrons it uses to bond with other atoms.
Chemists also guess that pure tennessine is a solid at normal room temperature. The most stable known type of this element is tennessine-294. This specific isotope has a half-life of just 51 milliseconds.
This means the new atom breaks apart almost as soon as it forms. It quickly shoots out energetic alpha particles to lose weight. This decay turns it into a lighter element called moscovium.
This extreme instability makes it impossible to study tennessine in large amounts. Today, scientists can only observe one single tennessine atom at a time.