|
Pauling's principle of electroneutrality states that each atom in a stable substance has a charge close to zero. It was formulated by Linus Pauling in 1948 and later revised.〔The Nature of the Chemical bond, L. Pauling, 1960, 3d edition, pp. 172-173, 270, 273, 547 Cornell University Press, ISBN 0-8014-0333-2〕 The principle has been used to predict which of a set of molecular resonance structures would be the most significant, to explain the stability of inorganic complexes and to explain the existence of π-bonding in compounds and polyatomic anions containing silicon, phosphorus or sulfur bonded to oxygen; it is still invoked in the context of coordination complexes.〔R.H. Crabtree, The Organometallic Chemistry of the Transition Metals, 6th edition, John Wiley & Sons, (e-book), ISBN 9781118788240〕 However, modern computational techniques indicate many stable compounds have a greater charge distribution than the principle predicts (they contain bonds with greater ionic character). ==History== Pauling first stated his "postulate of the essential electroneutrality of atoms" in 1948, at the Liversidge lecture (in a broad-ranging paper that also included his ideas on the calculation of oxidation states in molecules): :“...the electronic structure of substances is such as to cause each atom to have essentially zero resultant electrical charge, the amount of leeway being not greater than about +/- ½ , and these resultant charges are possessed mainly by the most electropositive and electronegative atoms and are distributed in such a way as to correspond to electrostatic stability." A slightly revised version was published in 1970: :“Stable molecules and crystals have electronic structures such that the electric charge of each atom is close to zero. Close to zero means between -1 and +1.”〔General Chemistry, Linus Pauling, 1988 p 192, Dover (reprint of 3d edition orig. pub. W.H. Freeman 1970), ISBN 0-486-65622-5〕 Pauling said in his Liversidge lecture in 1948 that he had been led to the principle by a consideration of ionic bonding. In the gas phase, molecular caesium fluoride has a polar covalent bond. The large difference in electronegativity gives a calculated ionic character of 9%. In the crystal (CsF has the NaCl structure with both ions being 6-coordinate) if each bond has 9% covalent character the total covalency of Cs and F would be 54%. This would be represented by one bond resonating between the six positions and the overall effect would be to reduce the charge on Cs to about + 0.5 and fluoride to -0.5. It seemed reasonable to him that such a reduction would be general.〔 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「Pauling's principle of electroneutrality」の詳細全文を読む スポンサード リンク
|