Xenon tetroxide
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Xenon tetroxide is a chemical compound of xenon and oxygen with molecular formula XeO4, remarkable for being a relatively stable compound of a noble gas. It is a yellow crystalline solid that is stable below −35.9 °C; above that temperature it is very prone to exploding and decomposing into elemental xenon and oxygen (O2).<ref name="selig">
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All eight valence electrons of xenon are involved in the bonds with the oxygen, and the oxidation state of the xenon atom is +8. Oxygen is the only element that can bring xenon up to its highest oxidation state; even fluorine can only give [[xenon hexafluoride|Template:Chem2]] (+6), though attempts to synthesize [[xenon octafluoride|Template:Chem2]] (+8) are still being made.
Two other short-lived xenon compounds with an oxidation state of +8, Template:Chem2 and Template:Chem2, are accessible by the reaction of xenon tetroxide with xenon hexafluoride. Template:Chem2 and Template:Chem2 can be detected with mass spectrometry. The perxenates are also compounds where xenon has the +8 oxidation state.
Reactions
At temperatures above Template:Convert, xenon tetroxide is very prone to explosion, decomposing into xenon and oxygen gases with ΔH = Template:Val:
Xenon tetroxide dissolves in water to form perxenic acid and in alkalis to form perxenate salts:
Xenon tetroxide can also react with xenon hexafluoride to give xenon oxyfluorides:
Synthesis
All syntheses start from the perxenates, which are accessible from the xenates through two methods. One is the disproportionation of xenates to perxenates and xenon:
The other is oxidation of the xenates with ozone in basic solution:
Barium perxenate is reacted with sulfuric acid and the unstable perxenic acid is dehydrated to give xenon tetroxide:<ref>Template:Cite book</ref>
Any excess perxenic acid slowly undergoes a decomposition reaction to xenic acid and oxygen:
References
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