Which element has atomic number 117?

Which element has atomic number 117? The answer is tennessine. Its atomic number means every tennessine atom contains 117 protons in its nucleus, which uniquely identifies the element.

Tennessine has the chemical symbol Ts and belongs to group 17, the halogen group. It is a synthetic, superheavy element and does not occur naturally in meaningful quantities. Scientists first announced its creation in 2010 through a collaboration involving the Joint Institute for Nuclear Research and several U.S. laboratories.

The name honors Tennessee, where important research institutions involved in the discovery are located. The International Union of Pure and Applied Chemistry officially approved the name in 2016.

A common mix-up is with nearby superheavy elements: nihonium is element 113, moscovium is 115, and oganesson is 118. Tennessine is element 117, immediately before oganesson in the periodic table.