Tennessine · element 117
A halogen on paper, a metal in theory, and it needed a berkelium target that almost got stuck in customs
Key facts
Tennessine is the most recently discovered element, first made in 2010, and its creation required an international relay. Berkelium-249, the target material, exists only in tiny amounts and decays with a half-life under a year, so it had to be made fresh at Oak Ridge in Tennessee and rushed to Dubna in Russia before too much of it disappeared. The package was refused entry twice over paperwork and crossed the Atlantic several times.
The name honours the state of Tennessee, home to Oak Ridge National Laboratory, Vanderbilt University and the University of Tennessee, which all contributed. Tennessine sits at the bottom of group 17, the halogens, which is why it ends in -ine like fluorine and chlorine. Whether it deserves to be called a halogen is another matter.
Where it is found
Tennessine does not exist in nature. Its isotopes decay in less than a tenth of a second, so no natural process could preserve it. Every atom has been made in an accelerator, and the total ever produced is of the order of a couple of dozen atoms since 2010.
Making it means firing calcium-48 at berkelium-249, and the berkelium is the hard part. Oak Ridge produced about 22 milligrams by irradiating curium in its High Flux Isotope Reactor for around 250 days, then spent months separating it chemically. Because berkelium-249 has a half-life of about 330 days, the clock ran from the moment it left the reactor. At Dubna the fused nuclei shed three or four neutrons to give tennessine-293 and 294.
How it was discovered
The collaboration was proposed by Joseph Hamilton of Vanderbilt University, who brought together Oganessian's team at Dubna, the reactor and chemistry expertise at Oak Ridge, and physicists from Livermore and the University of Tennessee. The Dubna experiment ran from 2009 into 2010 and detected six atoms, announced in April 2010. A second campaign in 2012 added more, and in 2014 GSI reproduced the result.
IUPAC recognised the discovery in December 2015 and approved the name tennessine, symbol Ts, in November 2016. It is only the second element named after a US state, after californium. The -ine ending was kept to match the rest of group 17, for consistency with tradition rather than as a claim about how tennessine actually behaves.
What we use it for
Tennessine has no uses. It decays in a few hundredths of a second and has been made only a couple of dozen times, so no chemistry experiment has been attempted.
Its scientific value is twofold. First, tennessine's decay chains pass through moscovium, nihonium, roentgenium, meitnerium and bohrium, and because these isotopes are neutron-rich they live longer than those made by other routes. Rising half-lives with neutron number are what the island of stability predicts, so tennessine's data help trace its shoreline. Second, tennessine tests the idea of a halogen. Fluorine and chlorine grab an electron to form negative ions. Calculations suggest tennessine would rather lose electrons than gain one, favouring +1 and +3 and behaving like a metal.
Reading the numbers
The atomic mass of 294 is the longest-lived isotope, which survives for a few tens of milliseconds. The physical values are calculations. A melting point near 723 kelvin, about 450 degrees Celsius, and a boiling point around 883 kelvin, about 610 degrees Celsius, would make tennessine a solid at room temperature and far less volatile than iodine. The predicted density of about 7.2 grams per cubic centimetre is above iodine's 4.9.
The configuration [Rn] 5f14 6d10 7s2 7p5 gives seven outer electrons, one short of a full shell, which defines group 17. In the lighter halogens that gap drives a hunger for one more electron. In tennessine, relativity splits the 7p shell into a tightly bound pair and a looser trio, and the trio is expected to be given up more easily than the gap is filled. Predictions therefore describe a metal forming compounds like TsCl rather than salts like NaTs.
Safety and the environment
Tennessine is radioactive and vanishes within a fraction of a second. It cannot be stored, transported or released, and the couple of dozen atoms ever produced were created inside shielded accelerator facilities and detected only by their decay. There is no tennessine in the environment and no conceivable route for public exposure.
Did you know?
- Tennessine is the most recently discovered element, first made in 2010, later than oganesson, nihonium and the rest of period 7.
- The berkelium-249 target, about 22 milligrams, took roughly 250 days of reactor irradiation at Oak Ridge to produce and had a half-life of only 330 days.
- The shipment of berkelium to Russia was twice refused by customs over paperwork and crossed the Atlantic several times before it arrived.
- Tennessine is the second element named after a US state, following californium, which was named in 1950.
- Despite ending in -ine like the other halogens, tennessine is predicted to behave more like a metal and is unlikely to form negative ions.
More in the halogens
These share a column with tennessine, so their outer electrons are arranged in a similar way and they tend to behave alike.
See all 6 halogens on one page, or browse all 118 elements. Also listed under the superheavy elements.
Frequently asked questions
Who is tennessine named after?
Not a person. Tennessine is named after the US state of Tennessee, home to Oak Ridge National Laboratory, Vanderbilt University and the University of Tennessee, all of which contributed to its discovery. The name was approved in 2016.
Is tennessine a halogen?
It sits in group 17 with the halogens and ends in -ine to match them, but calculations suggest it will not behave like one. Relativistic effects are predicted to make it more metallic, favouring +1 and +3 states rather than forming negative ions like chlorine or iodine.
What is the half-life of tennessine?
Very short. Tennessine-294, the longest-lived known isotope, survives for a few tens of milliseconds, and tennessine-293 for around twenty milliseconds. Both decay by alpha emission to moscovium.
How was tennessine made?
By firing a beam of calcium-48 ions at a target of berkelium-249 at the Dubna laboratory in Russia. The berkelium was produced at Oak Ridge in Tennessee, and the first six atoms were detected in 2010.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Tennessine reference article. Spotted an error? Tell us.