Xenon tetroxide is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
of
xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
and
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
with molecular formula XeO
4, remarkable for being a relatively stable
compound of a noble gas. It is a yellow
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
line
solid
Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structur ...
that is stable below −35.9 °
C; above that temperature it is very prone to exploding and decomposing into elemental xenon and oxygen (O
2).
[
]
All eight
valence electron
In chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair form ...
s of xenon are involved in the bonds with the oxygen, and the
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
of the xenon atom is +8. Oxygen is the only
element that can bring xenon up to its highest oxidation state; even
fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...
can only give
XeF6 (+6).
Two other short-lived
xenon compounds
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the f ...
with an oxidation state of +8, XeO
3F
2 and XeO
2F
4, are accessible by the reaction of xenon tetroxide with
xenon hexafluoride
Xenon hexafluoride is a noble gas compound with the formula XeF6. It is one of the three binary fluorides of xenon, the other two being XeF2 and XeF4. All known are exergonic and stable at normal temperatures. XeF6 is the strongest fluorinati ...
. XeO
3F
2 and XeO
2F
4 can be detected with
mass spectrometry
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is u ...
. The
perxenates are also compounds where xenon has the +8 oxidation state.
Reactions
At temperatures above −35.9 °C, xenon tetroxide is very prone to explosion, decomposing into xenon and oxygen gases with Δ''H'' = −643 kJ/mol:
:XeO
4 → Xe + 2 O
2
Xenon tetroxide dissolves in water to form
perxenic acid 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 ...
and in alkalis to form
perxenate salts:
:XeO
4 + 2 H
2O → H
4XeO
6
:XeO
4 + 4 NaOH → Na
4XeO
6 + 2 H
2O
Xenon tetroxide can also react with
xenon hexafluoride
Xenon hexafluoride is a noble gas compound with the formula XeF6. It is one of the three binary fluorides of xenon, the other two being XeF2 and XeF4. All known are exergonic and stable at normal temperatures. XeF6 is the strongest fluorinati ...
to give xenon oxyfluorides:
:XeO
4 + XeF
6 → XeOF
4 + XeO
3F
2
:XeO
4 + 2XeF
6 → XeO
2F
4 + 2 XeOF
4
Synthesis
All syntheses start from the
perxenates, which are accessible from the
xenates through two methods. One is the
disproportionation
In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. More generally, the term can ...
of xenates to perxenates and xenon:
: 2 + 2 OH
− → + Xe + O
2 + 2 H
2O
The other is oxidation of the xenates with
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the l ...
in basic solution:
: + O
3 + 3 OH
− → + O
2 + 2 H
2O
Barium perxenate is reacted with
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...
and the unstable perxenic acid is dehydrated to give xenon tetroxide:
: + 2 → 2 +
: → 2 +
Any excess
perxenic acid 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 ...
slowly undergoes a decomposition reaction to
xenic acid and oxygen:
: 2 → + 2 + 2
References
*
{{DEFAULTSORT:Xenon Tetroxide
Xenon(VIII) compounds
Inorganic compounds
Oxides