Tennessine ($Ts$)
The superheavy "halogen" named after the state of Oak Ridge—a synthetic anomaly where classical chemistry entirely breaks down.
Tennessine is the second-heaviest known element in the universe. It was discovered in 2010 through another extraordinary collaboration between the Russian JINR in Dubna, and American institutions including Vanderbilt University, the University of Tennessee, and the Oak Ridge National Laboratory (ORNL). In recognition of the indispensable role that the state's facilities played in its creation, the element was officially named Tennessine in 2016.
Occupying Group 17, Tennessine sits directly below Astatine. While the suffix "-ine" reflects its placement in the halogen group (Fluorine, Chlorine, Bromine, Iodine, Astatine), quantum chemistry tells a vastly different story. Tennessine represents the absolute breakdown of periodic trends, behaving more like a post-transition metal than a reactive, salt-forming gas.
Atomic & Radioactive Properties
Tennessine atoms exist for fractions of a second. Its macroscopic properties are completely theoretical, but it is predicted to be a dense, volatile, metallic solid.
| Property | Value |
|---|---|
| Atomic Number | 117 |
| Standard Atomic Weight | [294] |
| Electron Configuration | $[Rn] 5f^{14} 6d^{10} 7s^2 7p^5$ (Predicted) |
| Most Stable Isotope | 294Ts (Half-life: ~51 milliseconds) |
| Common Oxidation State | +1, +3 (Expected) |
| Density (Predicted) | 7.17 g/cm³ |
Synthesis: The 250-Day Campaign
The Half-Life Race
Synthesizing element 117 was an immense logistical challenge. The required target material, Berkelium-249, could only be produced at the High Flux Isotope Reactor at Oak Ridge. Producing just 22 milligrams of berkelium took a 250-day irradiation campaign.
However, Berkelium-249 has a half-life of only 330 days. As soon as it was produced, it was rushed to Russia, purified, and placed into the Dubna cyclotron to be bombarded with Calcium-48 before it decayed away into Californium.
Chemistry: The Halogen That Isn't
The defining characteristic of halogens is their desire to gain one electron to complete their octet (forming anions like $Cl^-$ or $I^-$). For Tennessine, this fundamental trait vanishes.
Theoretical calculations suggest that Tennessine will not form a $Ts^-$ anion under normal conditions. Furthermore, it will not exist as a diatomic molecule ($Ts_2$) like chlorine gas or solid iodine. Instead, the bonds between Tennessine atoms are predicted to be entirely metallic.
Spin-Orbit Coupling
Why does Tennessine betray its group? The answer is Spin-Orbit Coupling, an extreme relativistic effect.
In superheavy atoms, the massive nucleus forces the electrons to move at relativistic speeds. This causes the $7p$ orbital to "split" into two sub-levels: the highly stabilized $7p_{1/2}$ and the destabilized $7p_{3/2}$.
Because the single unpaired electron of Tennessine sits alone in the destabilized $7p_{3/2}$ sub-level, it is easily lost. Thus, instead of gaining an electron like a halogen, Tennessine strongly prefers to lose electrons, functioning primarily in the +1 or +3 oxidation states. It is the ultimate proof that relativity rewrites the rules of chemistry at the edge of the periodic table.
This is the 117th part of our "Elements and Their Properties" series. We are one element away from completing the table! To master the mathematics of spin-orbit coupling and relativistic subshell splitting, visit our Success Blueprint.
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