Atomic number 117

Tennessine

Ts
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117 electrons in 7 shells: 2, 8, 18, 32, 32, 18, 7.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Halogen
Period: 7
Group: 17
Block: p
Atomic mass: 294.211 Da (longest-lived isotope, estimated)
Electron configuration: [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵ (predicted)
Phase at 25 °C: solid (predicted)
Discovered: 2010, Joint Institute for Nuclear Research, Lawrence Livermore National Laboratory and Oak Ridge National Laboratory

Neighbours in the table

Tennessine is named for a US state. The name honours the Tennessee region, home to the University of Tennessee at Knoxville, Vanderbilt University and Oak Ridge National Laboratory, for its work on superheavy elements. Part of that work, IUPAC notes, was producing and chemically separating the actinide target materials such experiments need, at Oak Ridge’s High Flux Isotope Reactor and Radiochemical Engineering Development Center. The discoverers proposed the name jointly, IUPAC published it in June 2016, and after a five-month public review approved it on 28 November 2016.

Even the ending was set by rule. IUPAC gives new members of group 17 the suffix -ine, for historical and chemical consistency with the rest of the group. If the prediction holds, tennessine’s electrons sit at [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁵, across seven shells holding 2, 8, 18, 32, 32, 18 and 7. Its seven predicted outer electrons, 7s² 7p⁵, repeat the outer pattern of the halogens.

Its predicted oxidation states are −1, +1, +3 and +5 in Los Alamos’s listing, bookkeeping charges that treat each bond as if it were ionic. At room temperature the element is expected to be a solid, according to Jefferson Lab.

Where it is found

Tennessine has no stable isotope, in Jefferson Lab’s listing, and Oak Ridge calls it a synthetic element. Every known atom of it was made in a laboratory. Scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, announced it on 5 April 2010, in Jefferson Lab’s account. Lawrence Livermore and Oak Ridge National Laboratories were their partners.

The recipe was a beam of calcium-48 ions fired at berkelium-249. Oak Ridge supplied 22 milligrams of that berkelium, a byproduct of its californium-252 production. Berkelium-249 has a half-life of 330 days, so the target was losing atoms from the moment it left the reactor, and the discovery became a race against time. Three months of waiting and three of chemical separations came first.

The shipment to Russia was turned back to New York twice before it was accepted. In Dmitrovgrad, at the Research Institute of Atomic Reactors, the berkelium was hand-painted onto a target bound for JINR. Six months of bombardment there produced about six atoms of element 117, watched by detectors that Oak Ridge’s Rykaczewski had helped supply.

Why it matters

Element 117 was formally recognised on 30 December 2015. IUPAC found that the Dubna, Livermore and Oak Ridge experiments, begun in 2010 and confirmed in 2012 and 2013, met its criteria. Proof was hard to come by: such atoms decay into previously unknown isotopes of slightly lighter elements, which must also be identified beyond doubt, in the words of Paul J. Karol, who chaired the assessment. With elements 113, 115 and 118, tennessine completed the seventh row of the periodic table.

PubChem gives the mass of its longest-lived isotope, tennessine-294, 294.211 Da. Its half-life, the time for half of a sample to decay, is about 80 milliseconds in Jefferson Lab’s figure. The Atomic Mass Data Center gives 70 milliseconds, and the evaluation of the International Atomic Energy Agency (IAEA) gives 51. The isotope decays entirely by alpha emission, becoming moscovium-290. Tennessine-293 is shorter-lived, at 25 milliseconds in the centre’s figures.

Its predicted seven outer electrons place tennessine with the halogens. Outer-shell electrons largely set an element’s combining power, and elements of groups 15 to 17 tend to gain electrons, in Chem1’s account.

Properties

Properties of tennessine Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	117
Atomic mass	294.211 Da	Da	PubChem, longest-lived isotope, estimated
Electron configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p⁵ (predicted)
Phase at 25 °C	solid (predicted)

This element has no standard atomic weight; the atomic mass shown is that of its longest-lived isotope, as PubChem gives it.

That mass is an estimate by the IAEA's Atomic Mass Data Center, not a measurement.

The electron configuration and the phase of this element are predictions, not measurements.

Safety

Tennessine is radioactive: every isotope measured so far decays by alpha emission, in the Atomic Mass Data Center’s figures. Only a few atoms have ever been produced, in Jefferson Lab’s account, each gone within a fraction of a second, so there is none to handle. It has no use outside basic scientific research, and PubChem’s record for element 117 is the reference.

Questions

Why is the symbol for tennessine Ts?

IUPAC approved Ts together with the name on 28 November 2016; until then the element had the placeholder name ununseptium and the symbol Uus. Some chemists objected that Ts is already one of the two usual abbreviations for the tosyl group. IUPAC kept the symbol all the same, judging that the setting in which Ts appears leaves no doubt about which one a writer means.

What is the half-life of tennessine?

Tennessine-294, its most stable isotope in Jefferson Lab's words, has a half-life of roughly 80 milliseconds by Jefferson Lab's figure, 70 milliseconds by the Atomic Mass Data Center's and 51 milliseconds in the IAEA evaluation. It decays only by alpha emission, becoming moscovium-290 in Jefferson Lab's account. Tennessine-293 has a half-life of 25 milliseconds, and the centre lists estimated values of 10 and 2 milliseconds for tennessine-292 and tennessine-291.

Is tennessine a halogen?

It sits in group 17, and Jefferson Lab classes it as a halogen that is expected to be a solid. Its predicted configuration ends in 7s² 7p⁵, seven outer electrons, and IUPAC gave it the -ine ending reserved for group 17 names. Los Alamos predicts oxidation states of −1, +1, +3 and +5, an empirical radius of 138 pm and a melting range of 350 to 550 °C.

What is tennessine used for?

Nothing outside basic scientific research, according to Jefferson Lab, since only a few atoms of it have ever been produced. For Rykaczewski of Oak Ridge, who oversaw detectors lent to the Dubna experiment, the larger prize is progress toward long-lived synthetic nuclei, which he ranks above the addition of new elements. Such nuclei, in his view, might open new fields in physics and chemistry.