Xenon tetroxide
Encyclopedia
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 crystal
line solid
that is stable below −35.9 °C
; above that temperature it is very prone to explode, decomposing into xenon and oxygen (O2).
All eight valence shell electron
s 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 XeF6
.
The two other short lived xenon compounds
with an oxidation state of +8 are accessible by the reaction of xenon tetroxide with xenon hexafluoride
. XeO3F2 and XeO2F4 can be detected with mass spectrometry
.
s, which are accessible from the xenate
s 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:
The unstable perxenic acid slowly undergoes a disproportionation reaction to the xenic acid
and oxygen:
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
of xenon
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
with molecular formula XeO4, remarkable for being a relatively stable compound of a noble gas
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
. It is a yellow crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
line solid
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...
that is stable below −35.9 °C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
; above that temperature it is very prone to explode, decomposing into xenon and oxygen (O2).
All eight valence shell electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s of xenon are involved in the bonds with the oxygen, and the oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
of the xenon atom is +8. Oxygen is the only element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
that can bring xenon up to its highest oxidation state; even fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
can only give XeF6
Xenon hexafluoride
Xenon hexafluoride is a noble gas compound with the formula XeF6 and the highest of the three binary fluorides of xenon, the other two being XeF2 and XeF4. All are exergonic and stable at normal temperatures. XeF6 is the strongest fluorinating agent of the series...
.
Reactions
At temperatures above −35.9 °C, xenon tetroxide is very prone to explosion, decomposing into xenon gas and oxygen with ΔH = −643 kJ/mol:- XeO4 → Xe + 2 O2
The two other short lived xenon compounds
Noble gas compound
Noble gas compounds are chemical compounds that include an element from Group 18 of the periodic table, the noble gases.-History and background:...
with an oxidation state of +8 are accessible by the reaction of xenon tetroxide with xenon hexafluoride
Xenon hexafluoride
Xenon hexafluoride is a noble gas compound with the formula XeF6 and the highest of the three binary fluorides of xenon, the other two being XeF2 and XeF4. All are exergonic and stable at normal temperatures. XeF6 is the strongest fluorinating agent of the series...
. XeO3F2 and XeO2F4 can be detected with mass spectrometry
Mass spectrometry
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...
.
Synthesis
All syntheses start from the perxenatePerxenate
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°...
s, which are accessible from the xenate
Xenic acid
Xenic acid is a noble gas compound formed by the dissolution of xenon trioxide in water. Its chemical structure is H2XeO4. It is a very powerful oxidizing agent, and its decomposition is dangerous as it liberates a large amount of gaseous products—xenon, oxygen, and ozone.Its existence was...
s through two methods. One is the disproportionation
Disproportionation
Disproportionation, also known as dismutation is used to describe a specific type of redox reaction in which a species is simultaneously reduced and oxidized so as to form two different products....
of xenates to perxenates and xenon:
- 2 XeO42– → XeO64– + Xe + O2
The other is oxidation of the xenates with ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
in basic solution:
- XeO42– + O3 + 2 OH– → XeO64– + O2 + H2O
Barium perxenate is reacted with sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
and the unstable perxenic acid is dehydrated to give xenon tetroxide:
- + 2 → 2 +
- → 2 +
The unstable perxenic acid slowly undergoes a disproportionation reaction to the xenic acid
Xenic acid
Xenic acid is a noble gas compound formed by the dissolution of xenon trioxide in water. Its chemical structure is H2XeO4. It is a very powerful oxidizing agent, and its decomposition is dangerous as it liberates a large amount of gaseous products—xenon, oxygen, and ozone.Its existence was...
and oxygen:
- 2 → + 2 + 2