Which element with atomic number 118 is the heaviest recognized element? Oganesson is the answer.
Oganesson, symbol Og, has atomic number 118 and is currently the heaviest officially recognized chemical element. It occupies the final position in period 7 and is placed in group 18, alongside the noble gases. Its status as the heaviest element refers to the highest confirmed atomic number and atomic mass on the periodic table.
This element does not occur naturally in usable quantities. Scientists first synthesized it in 2002 at the Joint Institute for Nuclear Research in Dubna, Russia, in collaboration with researchers from the United States. Only a few atoms were made, and they survived for extremely short periods before radioactive decay.
The element was formally named oganesson in 2016 to honor nuclear physicist Yuri Oganessian, a leading figure in superheavy-element research. Its known isotope oganesson-294 has a half-life of roughly 0.7 milliseconds. Although it belongs to the noble-gas column, its chemistry has not been fully measured, so predictions about whether it behaves like lighter noble gases remain theoretical. A common mix-up is treating “heaviest” as meaning densest; the question concerns atomic number and mass, not measured density.