You may have thought Oganesson was a noble gas, but it will apparently readily react with Tennessine

[NNadir]

Here's the "facts:"

Relativistic effects for the superheavy reaction Og?+?2Ts2???OgTs4 (Td or D4h): dramatic relativistic effects for atomization energy of superheavy Oganesson tetratennesside OgTs4 and prediction of the existence of tetrahedral OgTs4

The paper seems to be open sourced, but here's an excerpt:

During the last decade, there have been numerous investigations of the superheavy elements (SHE) with Z?>?103 [1,2,3,4,5,6,7,8,9]. Recently [9], four superheavy elements (SHE) have been placed in the 7th row of the periodic table including the two heaviest SHE Tennessine Ts (Z?=?117) and Oganesson Og (Z?=?118). This is a landmark event for the scientists working in this area of research and should lead to a renewed interest in the experimental as well as theoretical investigation of the physical and chemical aspects of these heaviest SHE. It is well-recognized that there are problems with the experimental studies of the SHE, due to small production cross section, extra short lifetime, and the access of one atom at a time for chemical study, etc. However, except for a few diatomics of Ts and Og, there are hardly any ab initio all-electron relativistic and nonrelativistic calculations especially for systems of the two heaviest SHE Og and Ts. It is well-known that relativistic effects may be quite pronounced for atomic and molecular systems of SHE, and in the investigation of their electronic structure, bonding, chemical behavior, etc., Schrodinger’s nonrelativistic treatment may be inadequate while Dirac’s relativistic treatment for many-electron systems may be more appropriate for such systems. Dirac–Fock (DF) SCF theory for molecules was developed by Malli and Oreg [10] in 1975 and has been used extensively [11,12,13,14,15,16,17,18] to investigate the effects of relativity in the chemistry of heavy actinides, and superheavy elements. Recently, we have investigated [11,12,13,14,15,16,17,18] the effects of relativity on the electronic structure and bonding of numerous systems of heavy and superheavy elements (SHE). Our goal in this paper is to investigate the relativistic effects on the chemistry of Oganesson and especially for the atomization energies of Og (Ts)4 and energies of reaction for the superheavy reaction:

Og+2Ts2?OgTs4(TdorD4h) (1)...

Og is a congener of radium, tennessine a congener of iodine. Og and Ts are the heaviest elements synthesized thus far, the closest approach to the curious "Feynmanium" (undiscovered) element 137 where in theory the electrons would need to exceed the speed of light.

This paper will never be experimentally confirmed, but it's interesting from a calculational aspect. The OgTs4 molecule would have 584 electrons in its molecular orbital system.

Fun.

The chemistry of "noble" gases is well known. Xenon forms many different compounds with oxygen and fluorine, including some oxyanaions that can be complexed with super acids. Krypton has a well characterized fluoride. In ICP/MS analysis of iron, a molecular ion between argon and oxygen having a mass of 56 daltons can interfere with the iron isotope having that mass, special collision cells are necessary to break this complex.

[eppur_se_muova]

1. I may have mentioned this before, but ...

https://cris.tau.ac.il/en/publications/element-118-the-first-rare-gas-with-an-electron-affinity

It looks like it might be possible to prepare e.g. cesium oganesside -- can't access the full paper, so don't know if they did the full Hess cycle calc'n for that.

Beyond some Z, relativistic effects will give every neutral atom an electron affinity.