Tennessine is a superheavy artificial chemical element with an atomic number of 117 and a symbol of Ts. Also known as eka-astatine or element 117, it is the second-heaviest known element and penultimate element of the 7th period of the periodic table. As of 2016, fifteen tennessine atoms have been observed: six when it was first synthesized in 2010, seven in 2012, and two in 2014.
Three reasons Tennessine stands out
1
Named after US state known as the birthplace of blues.
2
It was first synthesised in 2010, making it one of the most recently confirmed elements on the periodic table.
3
Unlike the lighter halogens, it is predicted to have metallic rather than non-metallic properties due to relativistic effects.
A halogen unlike the halogens we can hold
Tennessine honors the Tennessee institutions that helped supply targets, data, and expertise for its discovery. It occupies the halogen column, but extreme relativistic effects may weaken the chemistry familiar from fluorine and chlorine. Every known atom has disappeared in a fraction of a second.
Recognizing Tennessine in Elementle
If Tennessine is the mystery element, guesses below atomic number 117 point up and guesses above it point down. Its symbol is Ts: a green letter matches the same position in that symbol, while a yellow letter belongs in another position.
The family clue turns green for halogen guesses. Compare Astatine (At), number 85 and Iodine (I), number 53: they share the family clue, but their atomic numbers and symbols help you tell them apart.
Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.
The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.