Oganesson (Og): the synthetic element with atomic number 118

Discovery and name

Oganesson was first reported from collaborative heavy-ion experiments in the early 21st century. Work at the Joint Institute for Nuclear Research in Dubna (Russia), with partner laboratories, led to the identification of the first atoms. The element has the distinctive label atomic number 118, making it the highest-numbered element confirmed so far. The name honors nuclear physicist Yuri Oganessian and was accepted by the international chemistry community after review.

Predicted physical and chemical properties

Because only a handful of atoms have been produced, most knowledge about oganesson comes from theoretical calculations. It is expected to complete the 7p electron shell, placing it in group 18, but very strong relativistic effects alter orbital energies and electron distribution. As a result, many predictions indicate oganesson may be much more polarizable and chemically reactive than lighter noble gases, perhaps behaving unlike a conventional inert gas. Its physical state at ambient conditions is uncertain; some calculations suggest it might be a dense solid rather than a monoatomic gas.

Isotopes, radioactivity and synthesis

All known oganesson nuclides are extremely unstable and decay rapidly, so the element is radioactive by necessity. The most commonly reported isotope in experiments is one with a mass number near 294. Atoms are produced in fusion reactions that join a heavy target nucleus with a lighter projectile; only a few atoms have been confirmed in repeated runs. Their lifetimes are measured in milliseconds or less and they decay by alpha emission and other short-range processes, making direct chemical study difficult.

Uses and scientific importance

There are no practical or commercial applications for oganesson because of its fleeting existence. Its value lies in fundamental science: synthesizing and characterizing the heaviest elements tests models of nuclear stability, shell effects, and relativistic quantum chemistry. Experiments and calculations involving oganesson inform periodic table limits and guide searches for longer-lived superheavy nuclides.

Notable facts and distinctions

• Oganesson is currently the highest-numbered element confirmed on the periodic table.
• Its placement in the noble-gas column contrasts with many theoretical predictions of atypical reactivity and electronic structure.
• Only a very small number of atoms have been synthesized, and research continues to refine the data on decay chains, lifetimes, and possible chemical behavior.

Researchers refer to ongoing theoretical work and scarce experimental data to better understand how extreme nuclear charge and relativistic effects shape the properties of the heaviest elements. For more general context about element synthesis and periodic trends, see related resources and reviews in nuclear and atomic physics.