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2 H2O <=> H3O+ + OH-
**The 2 NH3 <=> NH4+ + NH2-
*2 H2SO4 <=> H3SO4+ + HSO4-
*3 HF <=> H2F+ + HF2-
**Here proton transfer between two HF combines with homoassociation of and a third HF to form
2 PF5 <=> PF6- + PF4+
*N2O4 <=> NO+ + NO3-
** Here the nitrogen oxidation numbers change from (+4 and +4) to (+3 and +5).
*2 BrF3 <=> BrF2+ + BrF4-
These solvents all possess atoms with odd atomic numbers, either nitrogen or a halogen. Such atoms enable the formation of singly charged, nonradical ions (which must have at least one odd-atomic-number atom), which are the most favorable autoionization products. Protic solvents, mentioned previously, use hydrogen for this role. Autoionization would be much less favorable in solvents such as sulfur dioxide or carbon dioxide, which have only even-atomic-number atoms.
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, molecular autoionization (or self-ionization) is a chemical reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
between molecule
A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
s of the same substance to produce ions. If a pure liquid partially dissociates into ions, it is said to be self-ionizing. In most cases the oxidation number on all atoms in such a reaction remains unchanged. Such autoionization can be '' protic'' ( transfer), or ''non-protic''.
Examples
Protic solvents
Protic solvents often undergo some autoionization (in this case autoprotolysis): *self-ionization of water
The self-ionization of water (also autoionization of water, autoprotolysis of water, autodissociation of water, or simply dissociation of water) is an ionization reaction in properties of water, pure water or in an aqueous solution, in which a wa ...
is particularly well studied, due to its implications for acid-base chemistry of aqueous solutions.
*
Non-protic solvents
*Coordination chemistry
Autoionization is not restricted to neat liquids or solids. Solutions of metal complexes exhibit this property. For example, compounds of the type (where X = Cl or Br) are unstable with respect to autoionization forming .Kamata, K.; Suzuki, A.; Nakai, Y.; Nakazawa, H., "Catalytic Hydrosilylation of Alkenes by Iron Complexes Containing Terpyridine Derivatives as Ancillary Ligands", Organometallics 2012, 31, 3825-3828.See also
*Ionization
Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive Electric charge, charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged at ...
* Ion association
* Solvent system definition of acids and bases
References
Molecular physics {{chem-stub