Oganesson (Og)

Oganesson is listed in group 18, at the foot of the column that runs helium, neon, argon, krypton, xenon, radon. Everything in that column is an unreactive gas at room temperature. Element 118 is calculated to be neither.

That is the most interesting thing about it, and it is also the point at which a reference page has to be careful, because nothing about oganesson's physical or chemical behaviour has ever been measured. Roughly five or six atoms have existed, each for well under a millisecond. Its placement as a gas in reference tables is a convention inherited from its column, not an observation.

What the calculations actually say

Relativistic quantum chemistry makes several specific predictions about element 118, and they point consistently away from noble-gas behaviour.

• It should be a solid. Calculated boiling points cluster around 350 K, with substantial uncertainty, which would place oganesson as a solid or possibly a liquid at ordinary room temperature rather than a gas.
• It should attract an extra electron. Every other noble gas has an electron affinity of essentially zero or below — the closed shell has no room and no appetite. Oganesson is calculated to have a genuinely positive electron affinity, meaning a stable Og⁻ anion should exist. No noble gas does that.
• It should be reactive. Compounds with fluorine are predicted to be considerably more stable than the corresponding xenon and radon fluorides, which are themselves real substances.
• Its electron shells may barely exist as shells. This is the most striking result. In 2018 Paul Jerabek, Peter Schwerdtfeger and colleagues computed the electron localisation function for oganesson and found the nested concentric pattern that marks out shell structure in every other atom is smeared almost to invisibility. Spin–orbit splitting in the 7p subshell reaches around ten electronvolts, and the valence electrons approach the behaviour of a uniform gas — the Thomas–Fermi limit, an idealisation normally used as a crude approximation, arrived at here by an actual atom.

Each of those is the output of a calculation. The distinction is not pedantry: an element whose listed melting point, density and phase are all computed sits in a different epistemic category from one where somebody has put a thermometer in a beaker, and the difference should be visible on the page.

The claim that was invented

Element 118's first appearance in the literature was fraudulent.

In 1999 a group at Berkeley reported making it by firing krypton at a lead target, and reported element 116 as its decay daughter. When other laboratories could not reproduce the result, the Berkeley data were re-examined, and it emerged that decay chains had been inserted into the analysis software with no corresponding events in the raw detector files.

The paper was retracted in 2001 by all its authors except one. A formal investigative committee chaired by Robert Vogt concluded in 2002 that Victor Ninov had intentionally fabricated the data, and he was dismissed for scientific misconduct. Re-examination of his earlier work at Darmstadt turned up altered data there too, and the record-keeping was described by investigators as falling outside accepted standards for research.

The episode changed practice. Superheavy-element claims are now expected to survive independent replication and open scrutiny of raw event files before recognition, which is part of why later claims took a decade to be confirmed.

The real synthesis, and a second living namesake

Element 118 was genuinely made at Dubna, in collaboration with Livermore, by firing calcium-48 at a californium-249 target. The first atom was observed in 2002, with results published in 2006 and further atoms accumulated afterwards. Thirteen years then passed before the claim was ratified, in the same December 2015 round of decisions that settled the rest of the seventh row.

The name honours Yuri Oganessian, who was alive when it was chosen and still is — the second person, after Glenn Seaborg, to have an element named for him during his lifetime. The recognition is for the calcium-48 approach behind the five heaviest squares on the table, elements 114 to 118, and for the theoretical work on shell stabilisation that suggested where to look. Element 113, which sits just outside that run, was awarded to a cold-fusion experiment in Japan instead.

The ending -on follows group 18 convention. The result is a square occupied by a noble gas that theory says is neither noble nor a gas, bearing the name of a living man, at the end of a column it has almost nothing in common with.

Oganesson-294 has a half-life of about seven-tenths of a millisecond, which is the practical reason none of this can be checked. Every prediction above waits on an isotope that lasts long enough to be asked a question, and no such isotope is currently known or expected.