The Stranger That Broke a Dogma

Named the stranger for its rarity and for how thoroughly it had hidden in the air, xenon later overturned one of chemistry's confident beliefs. The noble gases had been held to be utterly inert, incapable of forming compounds at all, a dogma so firm it appeared in textbooks as settled fact. In 1962 the chemist Neil Bartlett showed that xenon would react with the powerful oxidiser platinum hexafluoride to form a genuine compound, and a family of xenon fluorides and oxides soon followed. The stranger thus proved the least inert of the inert gases and forced a rewriting of the rules of bonding. Xenon has no ancient tradition, but its story carries the lesson that even a name meaning outsider could not keep it forever aloof.

Bartlett's insight came from an unrelated observation: he had just shown that platinum hexafluoride was powerful enough to oxidise ordinary oxygen gas, and, noticing that xenon's first ionisation energy was almost identical to that of molecular oxygen, reasoned that if PtF6 could strip an electron from O2 it ought to do the same to xenon, a chain of reasoning that led directly to the compound now known as xenon hexafluoroplatinate. Later reanalysis showed his original product was actually a more complex mixture of xenon-platinum-fluorine compounds, but the central chemical fact, that a noble gas could be made to bond, stood, and it triggered a wave of noble-gas chemistry that within a year produced krypton and radon compounds too.