Tennessine: An Overview of Element 117
Tennessine, symbolized as Ts, is a synthetic chemical element with atomic number 117. It was officially recognized in 2016 and named after the state of Tennessee in the United States, a region prominent in superheavy element research. As a superheavy element, Tennessine is not found naturally on Earth and can only be produced in laboratories through nuclear fusion reactions.
Discovery and General Properties
Tennessine is positioned in Group 17 of the periodic table, making it the heaviest known halogen. Its electron configuration is theoretically predicted to be [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵. However, due to its extremely high atomic number, relativistic effects significantly influence its electronic structure and predicted chemical properties, causing them to deviate from trends observed in lighter halogens like chlorine or iodine.
Chemical Reactivity
Theoretical Predictions and Group Trends
As Tennessine is a synthetic element with an extremely short half-life (the longest-lived isotope, Tennessine-294, has a half-life of approximately 51 milliseconds), direct experimental observation of its chemical reactivity is currently impossible. All understanding of its chemical behavior is based on theoretical calculations and predictions.
Relativistic effects are particularly pronounced for Tennessine. These effects cause the 7s and 7p₁/₂ orbitals to contract and stabilize, while the 7p₃/₂ orbitals are destabilized and expanded. This leads to a predicted “inert pair effect” for the 7s electrons and a large energy gap between the 7p₁/₂ and 7p₃/₂ subshells.
Consequently, Tennessine is predicted to deviate significantly from the typical halogen trend of forming a stable -1 oxidation state. Instead, theoretical studies suggest that the +1 oxidation state might be the most stable, followed by +3 and +5. This behavior is more akin to p-block metals or metalloids than typical halogens. Tennessine is also predicted to be a semiconductor or even a poor metal, rather than a non-metal.
Interaction with Water and Air
Given that only a few atoms of Tennessine have ever been synthesized, and these exist for mere fractions of a second, any practical interaction with water or air is impossible. If macroscopic quantities of Tennessine could exist, theoretical predictions suggest it would be significantly less reactive than lighter halogens like fluorine or chlorine. Its predicted metallic or metalloid character and the relativistic stabilization of its valence electrons would likely result in low reactivity towards water and air, unlike the vigorous reactions seen with alkali metals or lighter, highly electronegative halogens.
Safety and Other Characteristics
Radioactivity
All known isotopes of Tennessine are intensely radioactive. This extreme radioactivity and its associated health risks are the primary safety considerations. The energy released during its rapid radioactive decay is substantial.
Toxicity
Due to its intense radioactivity and the theoretical prediction of it being a heavy element with metallic/metalloid characteristics, Tennessine would be considered highly toxic. However, experimental data on its chemical toxicity does not exist because stable, weighable quantities have never been produced.
Flammability
The concept of flammability, which describes a substance’s ability to burn or undergo combustion, does not apply to Tennessine. As an element produced in sub-picogram quantities that decays almost instantaneously, its primary hazard is its radioactivity, not its potential to ignite or sustain a flame.
Chemical Reactions Involving Tennessine
No chemical reactions involving Tennessine have ever been observed or conducted. The synthesis of Tennessine atoms occurs through nuclear fusion, where the nuclei of two lighter atoms combine to form a heavier nucleus. An example of the nuclear reaction used to produce Tennessine-294 is the bombardment of Californium-249 (²⁴⁹Cf) with Calcium-48 (⁴⁸Ca) ions:
²⁴⁹Cf + ⁴⁸Ca → ²⁹⁷Ts* → ²⁹⁴Ts + 3n (neutrons)
This process is a nuclear transformation, not a chemical reaction where atoms interact through their valence electrons.