Oganesson – facts and properties
- Symbol
- Og
- Atomic number
- 118
- Atomic mass
- 294 u
- Period
- 7
- Group
- 18
- Category
- unknown, probably noble gas
- Electron configuration
- [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶
- Valence electrons
- 8
- State at standard conditions
- expected to be a gas
- Discovered
- 2006
Oganesson has atomic number 118 and is the heaviest known element. It stands in group 18 below radon, so by position it is a noble gas, yet calculations predict different behaviour: probably a solid instead of a gas. With it, period 7 is full and the table of known elements has no gaps. The name honours the Russian nuclear physicist Yuri Oganessian.
Position in the periodic table
Occurrence and extraction
Oganesson occurs only in the laboratory. The one secure isotope, oganesson-294, has a half-life of less than a millisecond. Only a handful of atoms have been detected so far, and each was recognised by its decay chain.
The first experiments took place in 2002 and 2005 at Dubna, in collaboration with the Lawrence Livermore National Laboratory. A californium-249 target was bombarded with calcium-48, by the principle of hot fusion from the flerovium page. The californium came from Oak Ridge. The results appeared in 2006. The nucleus emits alpha particles and so turns through livermorium into flerovium, which undergoes fission or decays further to copernicium.
An earlier announcement did not hold. In 1999 the Lawrence Berkeley National Laboratory reported signs of the element, made by bombarding lead with krypton ions. Other laboratories could not repeat it. In 2001 Berkeley withdrew the claim after an internal investigation had shown that the events were not present in the raw data.
Yuri Oganessian, born in 1933, headed the Flerov Laboratory at Dubna. The name was fixed in 2016, during his lifetime. After seaborgium this is the second time an element received its name during the lifetime of the person honoured. The ending -on matches the other noble gases from neon to radon.
Properties and reactions
Oganesson is in period 7 and group 18, below radon, with xenon, krypton, argon, neon and helium above. The electron configuration [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p⁶ is predicted too, giving 8 valence electrons: two in the 7s and six in the 7p orbital. The atomic mass entry, 294 u, is the mass number of oganesson-294. All statements on melting point, boiling point and density come from calculations.
For oganesson a solid, not a gas, is expected. One calculation gives a melting point of about 50 degrees Celsius. The electron shell is very large and easily deformed, so the atoms attract each other strongly.
Relativistic effects are decisive. Spin-orbit coupling splits the 7p level so strongly that the familiar shell structure blurs: calculations show the electrons spread almost evenly, not in clearly separated shells as in radon. Oganesson should therefore be more reactive than any other noble gas. Fluorides such as OgF₂ and OgF₄ are predicted, similar to the xenon fluorides XeF₂ and XeF₄. It would then be a noble gas in name only. No measurement exists for any of it.
Oganesson poses no danger, because the few atoms decay at once.
Research and synthesis
Oganesson is researched only and has no application. Hot fusion, as described on the flerovium page, got the field this far, and with oganesson each of the 118 elements has its place. The name is settled, and the seventh period is filled.
For elements 119 and 120 the method no longer suffices, because the necessary targets are lacking. Other projectiles are used, such as titanium-50 or chromium-54. At the Lawrence Berkeley National Laboratory and at Dubna they have already produced livermorium isotopes, and searches for element 119 are under way in Japan and elsewhere. Neither element has been found so far. An element 119 would open an eighth period.
Chemistry with oganesson is not possible today. The half-life is under a millisecond, and only single atoms are made. Whether oganesson is solid at room temperature and forms fluorides can only be tested with longer-lived isotopes and more atoms.
Quick question
What is the atomic number of oganesson (Og)?
FAQ
Is oganesson a noble gas?
By position yes, since it stands in group 18. Calculations predict a solid that is more reactive than all other noble gases. This has not been measured.
What is oganesson named after?
After the Russian nuclear physicist Yuri Oganessian, who led the research at Dubna. The naming took place in 2016, in his lifetime.
How many elements are there?
With oganesson all 118 elements of the first seven periods are known and named. Whoever finds an element 119 opens an eighth period. So far nobody has managed it.