Oganesson is a synthetic, highly radioactive noble gas element. Only a few atoms have ever been made; its most stable isotope decays in milliseconds.
Oganesson (Og) is a synthetic, superheavy element with atomic number 118. It is placed in Group 18 (the noble gases) and period 7, directly below radon. Because it does not occur in nature, it is produced atom-by-atom in particle accelerators.
Og is made in fusion–evaporation reactions using a calcium-48 beam on a californium-249 target. A stylized route is:
\(^{249}\mathrm{Cf}(^{48}\mathrm{Ca},\,3n)\,^{294}\mathrm{Og}\)
The excited compound nucleus cools by neutron evaporation (\(3n\)) to yield the observed isotope \(^{294}\mathrm{Og}\).
Newly formed Og atoms recoil into a separator and are implanted into position-sensitive detectors. Identification uses time-correlated decay chains with characteristic energies and lifetimes (mainly \(\alpha\)-decay, sometimes spontaneous fission):
\(^{294}_{118}\mathrm{Og} \;\xrightarrow{\alpha}\; ^{290}_{116}\mathrm{Lv} \;\xrightarrow{\alpha}\; \cdots\)
Only a few isotopes near \(A\approx 294\) have been reported. Their half-lives are milliseconds (occasionally approaching the sub-second range), which is enough to register decay chains but far too short for bulk measurements or conventional chemistry.
Og belongs to the noble gas group, but theory predicts it may be much less inert than lighter noble gases due to strong relativistic effects that alter its electron shells. Some models even suggest unusually high polarizability and weak bonding interactions compared with typical noble gases.
Direct chemistry is not established. Calculations allow for weakly bound species and possibly neutral or cationic complexes under extreme conditions. If formal oxidation states were assigned, highly unusual positive states could be transiently accessible, but any such chemistry would occur at the single-atom level.
A commonly cited closed-shell form is [Rn] 5f14 6d10 7s2 7p6. However, spin–orbit splitting strongly divides the 7p subshell (\(7p_{1/2}\) vs. \(7p_{3/2}\)), which helps explain predictions of enhanced polarizability and reduced inertness compared with lighter noble gases.
Some theoretical studies predict that Og’s large mass and polarizability could make it condense more readily than lighter noble gases—potentially favoring a solid or very low-boiling liquid at standard conditions. This has not been experimentally confirmed due to the extreme scarcity and millisecond lifetimes.
Only a few atoms of Og are produced per experiment and they decay almost immediately. That makes it impossible to prepare macroscopic samples to measure density, melting point, or crystal structure. Most values you see in tables are theoretical estimates with significant uncertainty.
Yes. Og is a radiotoxic superheavy element. Although experiments use atom-scale quantities, work is conducted with remote handling, high-vacuum separators, appropriate shielding, HEPA-filtered ventilation, dosimetry, and compliant radioactive-waste protocols.