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For instance, argon, krypton, and xenon form clathrates with hydroquinone, but helium and neon do not because they are too small or insufficiently polarizable to be retained. [61] Neon, argon, krypton, and xenon also form clathrate hydrates, where the noble gas is trapped in ice. [62] An endohedral fullerene compound containing a noble gas atom
Argon Krypton Xenon Radon; ... Phase changes and critical properties. Physical property Helium Neon Argon Krypton Xenon Radon; Boiling point (°C) [2] −268.8: −245.9:
From the standpoint of chemistry, the noble gases may be divided into two groups: [citation needed] the relatively reactive krypton (ionisation energy 14.0 eV), xenon (12.1 eV), and radon (10.7 eV) on one side, and the very unreactive argon (15.8 eV), neon (21.6 eV), and helium (24.6 eV) on the other.
Air is the primary industrial source of purified argon products. Argon is isolated from air by fractionation, most commonly by cryogenic fractional distillation, a process that also produces purified nitrogen, oxygen, neon, krypton and xenon. [24] Earth's crust and seawater contain 1.2 ppm and 0.45 ppm of argon, respectively. [25]
These are helium, neon, argon, krypton, xenon, and radon. Noble gases have a full outer valence shell making them rather non-reactive species. [2] While these elements have been described historically as completely inert, chemical compounds have been synthesized with all but neon and helium. [3]
Another example is xenon hydride (Xe(H 2) 8), in which xenon pairs are trapped inside solid hydrogen. [35] Such clathrate hydrates can occur naturally under conditions of high pressure, such as in Lake Vostok underneath the Antarctic ice sheet. [36] Clathrate formation can be used to fractionally distill xenon, argon and krypton. [37]
Because of its scarcity, xenon is much more expensive than the lighter noble gases—approximate prices for the purchase of small quantities in Europe in 1999 were 10 €/L (=~€1.7/g) for xenon, 1 €/L (=~€0.27/g) for krypton, and 0.20 €/L (=~€0.22/g) for neon, [67] while the much more plentiful argon, which makes up over 1% by volume ...
The noble gases (helium, neon, argon, krypton, xenon and radon) were previously known as 'inert gases' because of their perceived lack of participation in any chemical reactions. The reason for this is that their outermost electron shells (valence shells) are completely filled, so that they have little tendency to gain or lose electrons.