Perxenate

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Chemical compound

title: "Perxenate" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["oxyanions", "salts", "xenon(viii)-compounds", "octahedral-compounds"] description: "Chemical compound" topic_path: "general/oxyanions" source: "https://en.wikipedia.org/wiki/Perxenate" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Chemical compound ::

In chemistry, perxenates are salts of the yellow xenon-containing anion . This anion has octahedral molecular geometry, as determined by Raman spectroscopy, having O–Xe–O bond angles varying between 87° and 93°. The Xe–O bond length was determined by X-ray crystallography to be 1.875 Å.

Synthesis

Perxenates are synthesized by the disproportionation of xenon trioxide when dissolved in strong alkali:{{cite book | title = Elements of the p Block |volume=9 |series=Molecular World | first1= Charlie |last1=Harding | first2= David Arthur |last2=Johnson | first3= Rob |last3=Janes | publisher = Royal Society of Chemistry | year = 2002 | isbn = 0-85404-690-9 | page = 93 :2 XeO3 (s) + 4 OH− (aq) → Xe (g) + (aq) + O2 (g) + 2 H2O (l)

When Ba(OH)2 is used as the alkali, barium perxenate can be crystallized from the resulting solution.

Perxenic acid

::figure[src="https://upload.wikimedia.org/wikipedia/commons/3/32/Perxenonsäure_Structural_Formula_V.1.svg" caption="Perxenic acid"] ::

Perxenic acid is the unstable conjugate acid of the perxenate anion, formed by the solution of xenon tetroxide in water. It has not been isolated as a free acid, because under acidic conditions it rapidly decomposes into xenon trioxide, water, and oxygen gas: :

Its extrapolated formula, H4XeO6, is inferred from the octahedral geometry of the perxenate ion () in its alkali metal salts.

The pKa of aqueous perxenic acid has been indirectly calculated to be below 0, making it an extremely strong acid. Its first ionization yields the anion , which has a pKa value of 4.29, still relatively acidic. The twice deprotonated species has a pKa value of 10.81.{{cite book | title = Advances in Inorganic Chemistry | volume = 46 | author1 = John H. Holloway | author2 = Eric G. Hope | editor = A. G. Sykes | publisher = Academic Press | year = 1998 | isbn = 0-12-023646-X | page = 67

Properties

Perxenic acid and the anion are both strong oxidizing agents, capable of oxidising silver(I), copper (II) and manganese(II) to (respectively) silver(III), copper(III), and permanganate.{{cite book | title = General Chemistry | author = Linus Pauling | edition = 3rd | publisher = Courier Dover Publications | year = 1988 | isbn = 0-486-65622-5 | page = 251 | url-access = registration | url = https://archive.org/details/generalchemistry00paul_0/page/251

The sodium, potassium, and barium salts are soluble.{{cite book | title = Concise encyclopedia chemistry | author = Thomas Scott | author2 = Mary Eagleson | publisher = Walter de Gruyter | year = 1994 | isbn = 3-11-011451-8 | page = 1183 | title = Elements of the p block | author = Charlie Harding | author2 = David Arthur Johnson | author3 = Rob Janes | location = Great Britain | publisher = Royal Society of Chemistry | year = 2002 | isbn = 0-85404-690-9 | pages = 92–93 : Ba2XeO6 (s) + 2 H2SO4 (l) → XeO4 (g) + 2 BaSO4 (s) + 2 H2O (l)

Most metal perxenates are stable, except silver perxenate, which decomposes violently.{{cite book | title = Standard Potentials in Aqueous Solution | author = Allen J. Bard | author2 = Roger Parsons | author3 = Joseph Jordan | author4 = International Union of Pure and Applied Chemistry | publisher = CRC Press | year = 1985 | isbn = 0-8247-7291-1 | page = 778 | url = https://archive.org/details/standardpotentia0000unse/page/778

Applications

Sodium perxenate, Na4XeO6, can be used for the analytic separation of trace amounts of americium from curium. The separation involves the oxidation of Am3+ to Am4+ by sodium perxenate in acidic solution in the presence of La3+, followed by treatment with calcium fluoride, which forms insoluble fluorides with Cm3+ and La3+, but retains Am4+ and Pu4+ in solution as soluble fluorides.

References

References

  1. {{Holleman&Wiberg
  2. (March 1970). "Vibrational spectra and structures of xenate(VI) and perxenate(VIII) ions in aqueous solution". Inorganic Chemistry.
  3. (Aug 1963). "Geometry of the Perxenate Ion". Science.
  4. (October 1988). "Protolytic properties of perxenic acid". Inorganic Chemistry.
  5. {{Holleman&Wiberg
  6. (March 1965). "Analytical Oxidation of Americium with Sodium Perxenate". Analytical Chemistry.
  7. {{Cotton&Wilkinson6th

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oxyanionssaltsxenon(viii)-compoundsoctahedral-compounds