Ts · Element 117 · Halogen
The second-to-last gap in the seventh period, filled in 2010 with a berkelium target.
Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where tennessine sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Same element, different neutrons
All tennessine atoms have the same number of protons, 117, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Ts-294, has 177 neutrons and a half-life of 51 ms.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Ts-293 | 176 | — | 21 ms | α, SF |
| Ts-294 longest-lived | 177 | — | 51 ms | α |
Here the classroom shortcut, rounded atomic mass (294) minus atomic number, gives the same answer: 177.
Decay modes
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Size, to scale
Radius 247 pm — that is 0.247 nm, so about 2.02 million of them side by side would span a millimetre.
Thermal range
Tennessine is liquid over a 260 K window, from 623 K to 883 K.
Where it sits
Tennessine sits in period 7, group 17. Everything in group 17 shares the same outer-electron count, which is why they behave so similarly.
Other halogens
All halogensThe story
The second-to-last gap in the seventh period, filled in 2010 with a berkelium target.
International Collaboration: Tennessine discovery represents a major achievement in Russian-American scientific cooperation, combining JINR's expertise in superheavy element synthesis with Oak Ridge's unique capabilities in rare actinide target preparation.
Two-Year Intensive Campaign: The tennessine discovery required two years of very challenging experimentation from 2010 to 2012, involving the most sophisticated nuclear synthesis techniques ever attempted and achieving success rates of only individual atoms per week.
Oganessian Team Leadership: Led by Yuri Oganessian at the Joint Institute for Nuclear Research in Dubna, Russia, the discovery team overcame seemingly impossible technical challenges to create and identify the heaviest halogen ever synthesized.
Oak Ridge Critical Contributions: Oak Ridge National Laboratory provided the extremely rare berkelium-249 target material essential for tennessine synthesis, representing one of the most challenging target preparation achievements in nuclear physics history.
Technical Innovation: Creating tennessine required developing new ion beam optimization techniques, ultra-sensitive particle detection systems, and important data analysis methods that advanced the entire field of superheavy element research.
IUPAC Recognition: The International Union of Pure and Applied Chemistry officially recognized the discovery in 2015, granting naming rights to the discovery team. "Tennessine" honors Tennessee, home state of Oak Ridge National Laboratory.
Historic Scientific Achievement: Tennessine's discovery represented humanity's first successful synthesis of element 117, filling a crucial gap in the periodic table and demonstrating that even the most challenging scientific goals can be achieved through international cooperation.
Applications
Halogen Chemistry Investigation: Tennessine represents the heaviest known halogen, offering new opportunities to study how relativistic effects influence halogen chemistry. Theoretical predictions suggest tennessine might exhibit metallic properties despite being in group 17, challenging traditional chemical understanding.
Superheavy Element Synthesis Research: Tennessine creation through berkelium-249 bombardment with calcium-48 provides crucial insights into optimal nuclear reaction conditions for synthesizing the heaviest possible elements, advancing techniques for future periodic table exploration.
Nuclear Stability Studies: As element 117, tennessine occupies a unique position for studying nuclear shell effects and stability patterns in superheavy elements. Its decay characteristics provide valuable data about nuclear forces and stability mechanisms.
Relativistic Quantum Chemistry: Tennessine offers exceptional opportunities to test theoretical models of atomic structure under harsh conditions, particularly calculations predicting how relativistic electron orbital effects influence chemical bonding in superheavy elements.
Advanced Detection Technology: Creating and identifying tennessine requires the most sophisticated particle detection systems available, driving innovation in nuclear instrumentation that benefits multiple scientific fields from medical imaging to space exploration.
International Scientific Collaboration: Tennessine research exemplifies global cooperation in fundamental science, with teams from Russia, the United States, and other nations combining expertise and resources to achieve seemingly impossible scientific goals.
Future Applications Foundation: While currently limited to research, understanding tennessine's properties contributes to the long-term scientific goal of discovering stable superheavy elements that might transform technology in ways currently unimaginable.
Particle Accelerator Experiments: Tennessine exists only within highly specialized nuclear physics facilities equipped with the most powerful ion accelerators available. Creating tennessine requires months of continuous operation to produce just a few atoms, making each synthesis a remarkable achievement.
Nuclear Reaction Mechanism Studies: Scientists use tennessine synthesis to understand heavy-ion fusion processes and nuclear reaction dynamics at very high energies, advancing fundamental knowledge of nuclear physics and reaction mechanisms.
Theoretical Chemistry Validation: Tennessine provides experimental data to test quantum mechanical predictions about superheavy element chemistry, particularly theories suggesting unusual chemical behavior for the heaviest halogens.
Advanced Instrumentation Innovation: Tennessine detection drives development of new particle identification systems, timing electronics, and data acquisition methods that benefit broader scientific research including materials science and medical physics.
Scientific Training Excellence: Tennessine experiments provide rare training opportunities for nuclear physicists and graduate students, advancing human expertise in superheavy element science and advanced nuclear research techniques.
International Research Coordination: Tennessine studies facilitate collaboration between world-leading nuclear physics laboratories, fostering knowledge sharing and technological advancement across international boundaries.
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
No Natural Existence: Tennessine has never been found in nature. Its 117-proton nucleus is far too unstable to survive in nature.
Exclusively Laboratory Creation: Every known tennessine atom has been artificially created through nuclear fusion reactions in the advanced particle accelerators. The process requires bombarding berkelium-249 targets with calcium-48 ions, achieving success rates of only one or two atoms per week.
Cosmic Absence: It is an open question whether the r-process in neutron star mergers briefly makes tennessine nuclei; none could survive. The element's extremely short half-life ensures that any hypothetically formed tennessine would decay before detection.
Ultra-Specialized Facility Requirement: Tennessine has been produced only in a few nuclear physics laboratories, particularly the Joint Institute for Nuclear Research in Dubna, Russia, where it was made by firing calcium-48 ions at a berkelium-249 target produced at Oak Ridge National Laboratory in the United States.
Fundamental Nuclear Instability: Tennessine's synthetic nature stems from basic nuclear physics principles. As proton number increases far beyond natural limits, electromagnetic repulsion between protons completely overwhelms the strong nuclear force that holds atomic nuclei together.
Future Production Prospects: While future accelerator technologies might eventually improve tennessine synthesis efficiency, the element will always remain artificial due to its inherent nuclear instability and extremely rapid radioactive decay.
Handling
Tennessine is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Atom-by-Atom Production: Tennessine is made a few atoms at a time in heavy-ion accelerators. Only single atoms have ever been made, and no weighable amount has ever existed.
Half-Lives: Its two known isotopes, tennessine-293 and tennessine-294, decay mainly by alpha emission with half-lives measured in milliseconds.
No Meaningful Dose: Each decay emits an alpha particle of about 11 MeV, an energy far too small to harm anyone when only single atoms exist.
Where the Hazards Are: The hazards in this research come from the experiment, not the element: the accelerator beam, radioactive targets and activated equipment, and the waste these produce, which is managed as radioactive waste under national radiation protection rules.
Worker Protection: Staff follow the standard occupational radiation rules: annual dose limits, personal dose monitoring and keeping doses as low as reasonably achievable. Workers under 18 face much lower dose limits than adults: one tenth of the adult limits under US Nuclear Regulatory Commission rules (10 CFR 20.1207), and 1 mSv a year at US Department of Energy laboratories (10 CFR 835.207). A worker who declares a pregnancy is limited to 5 mSv to the fetus over the whole pregnancy (10 CFR 20.1208 and 835.206).
Quick answers
Tennessine (symbol Ts) is element 117 on the periodic table, a halogen in period 7, group 17. The second-to-last gap in the seventh period, filled in 2010 with a berkelium target. At room temperature it is expected to be a solid, and it is radioactive.
[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵, giving 7 occupied shells with the distribution 2, 8, 18, 32, 32, 18, 7. Its outer shell holds 7 electrons, which is what sets its bonding behaviour.No sample of tennessine has ever been condensed, so both figures are calculated rather than measured: it is predicted to melt at 623 K (349.9 °C) and boil at 883 K (609.9 °C).
Tennessine has no stable isotope, so it has no standard atomic weight. The figure quoted, 294, is the mass number of its longest-lived known isotope.
Tennessine has no stable isotope. Its longest-lived known isotope, Ts-294, has 177 neutrons (mass number 294 minus atomic number 117) and a half-life of 51 ms. The classroom shortcut, rounded atomic mass (294) minus atomic number, gives the same 177.
Tennessine is predicted to have a density of about 7.2 g/cm³, though no sample large enough to weigh has ever been made. Water is 1.0 g/cm³ for comparison.
Tennessine was discovered in 2010 by JINR, Oak Ridge & Livermore. Origin of the name: Tennessee.
Tennessine does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.
Yes. Tennessine has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.