Og · Element 118 · Noble gas
Oganesson (Og) is element 118, a synthetic, radioactive member of group 18. Scientists have detected individual atoms through their decay; bulk properties such as its melting point are predictions. [1] [4]
Answers
Oganesson is radioactive. Experiments produce individual atoms that decay extremely quickly, not a lasting sample that could be handled or used in an ordinary product. That is different from saying the material is harmless. [1] [2]
No natural occurrence has been confirmed. The observed atoms were made in nuclear reactions in a laboratory. Claims that oganesson cannot exist anywhere in the universe go beyond that evidence. [1]
The observed isotope oganesson-294 starts its decay chain by emitting an alpha particle, becoming livermorium-290. Alpha emission removes two protons and two neutrons, so both atomic number and mass number decrease. [2] [1]
The NNDC evaluation gives a half-life of about 0.58 milliseconds, with substantial uncertainty. A half-life describes a statistical decay rate, not an exact lifetime for every atom. Og-294 has 118 protons and 176 neutrons, calculated as 294 minus 118. [2]
A neutral oganesson atom has 118 electrons. Its conventional predicted ground-state configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶. Grouping these orbitals by principal shell gives seven occupied shells, with 2, 8, 18, 32, 32, 18 and 8 electrons. [3]
This shell count is a model for organizing electrons. It is not a photograph of seven rings, and it does not imply that oganesson behaves chemically just like the lighter noble gases. [4]
Group 18 is called the noble gases, but that name does not establish oganesson’s physical state. Bulk oganesson has not been observed. A 2020 calculation predicts a melting point of 325 ± 15 K and a normal boiling point of 450 ± 10 K, suggesting a solid at ordinary room temperature. [4]
The density value near 7.2 g/cm³ is also theoretical, calculated at 319 K in that study. It is not a measured room-temperature density. Treat the prediction markers in the property table as part of the values. [4]
Structure
The visualization is an illustrative orbital model, not an experimental map of oganesson’s electrons. Its electron structure is predicted, and relativistic effects make it different from the lighter noble gases. Drag to rotate. [4]
Properties and predictions
Every bar shows where oganesson sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Same element, different neutrons
All oganesson atoms have the same number of protons, 118, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Og-294, has 176 neutrons and a half-life of 0.58 ms.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Og-294 longest-lived | 176 | — | 0.58 ms | α (observed) |
Here the classroom shortcut, rounded atomic mass (294) minus atomic number, gives the same answer: 176.
Only alpha decay has been observed for Og-294. The evaluated spontaneous-fission value is an upper limit of 20%, not an observed 20% decay branch. The table therefore identifies alpha as the observed mode. [5]
Decay modes
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Size, to scale
No atomic radius has been measured for oganesson. This illustration uses an estimated radius, not an experimental measurement. [3]
Thermal range
The phase boundaries shown are predictions: melting at 325 ± 15 K and boiling at 450 ± 10 K. No bulk sample has been observed changing phase. [4]
Where it sits
The story
Oganesson is a synthetic element whose identification rests on nuclear decay measurements. Its place at atomic number 118 is experimentally established; a visible bulk sample, melting point and boiling point are not. The bulk values shown here are calculations. [1] [4]
The observed isotope Og-294 contains 118 protons and 176 neutrons. It begins an alpha-decay chain by becoming Lv-290. Its evaluated half-life is about 0.58 ms. [2]
Oganesson was first made in 2002 at the Joint Institute for Nuclear Research in Dubna, Russia, by a Russian and American team led by Yuri Oganessian, with scientists from Lawrence Livermore National Laboratory in California. They bombarded californium-249 with calcium-48 ions and detected the decay of one atom of oganesson-294, possibly two, in 2002, and two more in 2005. The results were published in 2006.
In 1999 a team at Lawrence Berkeley National Laboratory reported element 118 from a reaction of lead and krypton. Other laboratories could not repeat the result, and in 2001 the claim was withdrawn; in 2002 an investigation concluded that the data had been fabricated by one of the researchers.
In December 2015 the joint working party of IUPAC and IUPAP recognized the Dubna and Livermore team as the discoverers. The name oganesson, symbol Og, was approved in November 2016. It honors Yuri Oganessian, the nuclear physicist who led much of the work on the heaviest elements. He was alive when the name was approved, which had happened only once before, when seaborgium was named after Glenn Seaborg in 1997. The ending -on follows the pattern of the other noble gases, such as argon and xenon.
Applications
Oganesson is studied in research on superheavy nuclei, radioactive decay and nuclear stability. It has no established consumer or industrial application. Individual atoms produced in experiments do not provide a lasting bulk sample. [1]
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
There is no confirmed natural occurrence of oganesson. The observed atoms have been made in laboratory nuclear reactions. That evidence does not establish what may be produced fleetingly in every astrophysical environment. [1]
The reported synthesis used calcium-48 ions and a californium-249 target. Scientists identified the resulting atoms through their characteristic alpha-decay sequences. [1]
Handling
Oganesson is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Oganesson is radioactive and has no known stable isotope. Its extremely short-lived experimental production is different from handling a bulk chemical sample. This does not establish that the element or its production process is harmless. [2] [1]
Its synthesis takes place in specialized nuclear research facilities using accelerated ions and radioactive target material. This reference page is not a handling procedure. [1]
Sources checked .
Laboratory synthesis, individual atoms, detection through alpha-decay chains and research context.
ENSDF evaluation, 2019. Half-life 0.58 ms with +0.44/-0.18 ms uncertainty; daughter Lv-290. Neutron count is derived from mass number minus atomic number.
Element identity, group, period and conventional electron configuration. This page’s half-life and bulk-state labels are not used here.
Original 2020 computational study, Oganesson: A Noble Gas Element That Is Neither Noble Nor a Gas. These are theoretical bulk-property estimates.
ENSDF adopted levels, page 2. Only alpha decay has been observed; spontaneous fission has an upper limit of 20%, not a measured branch.