Russian and US physicists have finally created element 117 - a superheavy element made of atoms containing 117 protons that is roughly 40 percent heavier than lead.
The achievement fills the final gap in the list of observed elements up to element 118.
The team produced the elusive element 117 by fusing together atoms of calcium and a rare, heavy element known as berkelium.
After smashing calcium atoms into a target of berkelium in a particle accelerator at the Joint Institute for Nuclear Research in Dubna, Russia, the team deduced the fleeting existence of element 117 by studying the daughter particles emitted as the atom decayed.
Like all superheavy atoms, element 117 is unstable, lasting only fractions of a second before self-destructing in a cascade of lighter elements and particles.
However, it still lasts longer than many lighter elements, confirming theories that predict that 117 and its recently-synthesized cousins, elements 116 and 118, exist in an island of stability on the periodic table. Only synthesizing increasingly heavy elements will show just how far the stable region extends up the list of elements.
While there's no known practical application for such short-lived atoms, the synthesis of superheavy elements is vital for testing models that explain how the neutrons and protons that make up all the elements bind together.
Since 1940, 26 new elements beyond uranium have been added to the periodic table.
he research will appear in Physical Review Letters.