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Molecular autoionization (or self-ionization) is a reaction between molecules of the same substance to produce ions. If a pure liquid partially dissociates into ions, it is said to be self-ionizing.〔Housecroft C.E. and Sharpe A.G. ''Inorganic Chemistry'' (2nd ed., Pearson 2005) p.163 ISBN 0130-39913-2〕 The oxidation number on all atoms in such a reaction remains unchanged. Such autoionization can be ''protic'' (H+ transfer), or ''non-protic''. Some examples of each are: Protic solvents: 2 H2O H3O+ + OH−. The self-ionization of water is particularly well studied, due to its implications for acid-base chemistry of aqueous solutions. 2 NH3 NH4+ + NH2− 〔Housecroft and Sharpe p.217〕 2 H2SO4 H3SO4+ + HSO4− 〔Housecroft and Sharpe p.223〕 3 HF H2F+ + HF2− 〔Housecroft and Sharpe p.221〕 Here proton transfer between two HF combines with homoassociation of F− and a third HF to form HF2−. Non-protic solvents: 2 PF5 PF6− + PF4+ 2 N2O4 NO+ + NO3− 〔 2 BrF3 BrF2+ + BrF4− 〔Housecroft and Sharpe p.224〕 The self-ionization 2 SO2 SO32− + SO2+ has also been proposed, but must be considered improbable because it would require the separation of doubly charged ions.〔 Molecular autoionization can occur in gases or solids, but occurs most readily in liquids. In gases, the molecules are so far apart that ion formation is very unfavorable, and in solids, there is not enough molecular movement. As long as the phase remains constant, autoionization normally increases substantially with increasing pressure. ==See also== *Ionization *Ion-association 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Molecular autoionization」の詳細全文を読む スポンサード リンク
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