![]() The idea that the noble-gas configuration is a particularly favorable one which can be achieved through formation of electron-pair bonds with other atoms is known as the octet rule. "Noble Gas" Valence Electron Configurations The sharing of electrons in this way between atoms means that more electrons are effectively “seeing” more nuclei, which you should remember is always the fundamental energetic basis of bond formation. This is not because of any mysterious properties of octets (or of noble gas atoms) it simply reflects the fact that filling an existing s-p valence shell is energetically more favorable than placing electrons in orbitals of higher principal quantum number. Present-day shared electron-pair theory is based on the premise that the octet in the outermost shells of the noble gas elements above helium represents a particularly favorable configuration. Lewis sought a way of achieving this octet in a way that did not involve ion formation, and he found it in his shared electron-pair theory published in 1916. It was also realized that elements known to form simple ions such as Ca 2+ or Cl – do so by losing or gaining whatever number of electrons is needed to leave eight in the valence shell of each. Atomic orbitals had not yet been thought of, but the concept of “valence” electrons was known, and the location of the noble gases in the periodic table suggested that all except helium posses eight valence electrons. This seemed satisfactory for compounds such as NaCl that were known to dissociate into ions when dissolved in water, but it failed to explain the bonding in non-electrolytes such as CH 4. Both scientists had earlier been involved in developing the cubical atom model which Lewis formulated in 1902 and which eventually led to the octet rule.Īt the time Lewis began developing his ideas in 1902, it was widely believed that chemical bonding involved electrostatic attraction between ion-like entities. ![]() Two interesting articles about them can be found at the Chemical Heritage Foundation site and at this Chemical Achievers site. Lewis and Langmuir were probably the two greatest American chemists of the first half of the twentieth century. He originated the concept of "seeding" clouds to induce precipitation- a field of sufficient public interest at the time to get him on the cover of Time Magazine in 1950. His most notable work was on the chemistry of surfaces and monomolecular layers. Irving Langmuir (1881-1967, Nobel Prize 1932) was an industrial scientist employed by the General Electric Co. His other notable work included acid-base theory, the thermodynamics of solutions, the first isolation of heavy water (D 2O), and the phosphorescence and magnetic properties of molecules.Īlthough Lewis originated the idea of the electron-pair bond, much of the credit for its early acceptance must go to Irving Langmuir, who extended it somewhat and enthusiastically popularized it to the extent that it began to be known as the Lewis-Langmuir theory, and even (to Lewis' annoyance) as the “Langmuir theory”. Lewis (1875-1946) created the College of Chemistry at the University of California, Berkeley, and made it into one of the world’s most productive centers of chemistry research. Lewis, whose 1902 lab notes eventually led to his classic article The Atom and the Molecule in 1916. The first really successful theory of chemical bonding was formulated by G.N. ![]() Lewis preached the gospel of shared electron-pairs to the unwashed multitudes.
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