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ROGERR. FESTA Northeast Missouri State University Kirksville. Mo. 63501
Gilbert Newton Lewis and the Amazing Electron Dots Naialle Fooie Tiernan Warren Township High School Gurnee. IL 60031
The electron dot formulas used in the teaching of valence and hondine are one of the most effective instructional tools employed in introductory chemistry. This scheme was develoned hv G. N. Lewis of the Universitv of California a t ~ e r c e l esince ~ . the electron dot diagrams i l l remain with the students throuehout their formal studv of chemistrv. it seemed wonhwh;le to in\.estigate the originof this model more thorounhlv. What ememed. however. wai the prufile of a most d i s t i n i ~ i ~ h ecdh e m i s t h d educator. As a Gather of introductory chemistry, the author believes that a review of the life and achievements of Lewis can enrich the curriculum in a singular and inspiring manner. Gilbert Newton Lewis was horn on October 23,1875, the middle child of attorney Francis Wesley Lewis and Mary Burr (White) Lewis. His father, a native of New Hampshire and a graduate of Dartmouth, took the family from Weymouth, Massachusetts, where Lewis had been horn, to Lincoln, Nebraska when Lewis was nine. Lewis taught himself to read at the age of three, but he did not attend school until age 13 when heentered thr preparatory school of the L'oiversitv of Nehrilska. He would have eraduated from the university with his classmate, Willa ~ a & e r in , 1895 if he had not transfered to Harvard as a iunior. Althoueh he developed a strong interest in economics; he took his EA in chemistry. He taught the following year a t the Philips Academy, Andover, while completing his master's degree a t Harvard. Then, returning to the university to study with T. W. Richards, he received the PhD in chemistry in 1899. Lewis remained an additional vear as an instructor at Harvard before accepting a fellowshipto study with Wilhelm Ostwald and Walther Nernst in Germanv. Followine this orestieious internship, he returned to his k r u c t o r s G p a t ~ a r v a ; dI. t was in 1902. durinn his tenure on the Harvard facultv. that Lewis first hegan d e h o p i n g his octet theory. Lewis' first mper. hmrd on his doctoral dissertation, was published in i898 and dealt with electrochemical and thermochemical properties of solutions of zinc and cadmium in mercury. In 1904, Lewis was appointed superintendent of weights and measures in the Philippine Islands and chemist in the Bureau of Science in Manila. Both positions gave him much time for laboratory research. The following year he joined the physical chemistry laboratory of Arthur Amos Noyes a t the Massachusetts Institute of Technology, where he was nromnted from assistant nrofessor to full ~rofessorin less than five years. Lewis married Marv Hincklev Sheldon..dauehter of Edward Stevens Sheldon, professor of &mance languages a t Harvard,
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Rofiles h Chemistry is a biographical feature highlighting the conhibulions of distinguished chemists in me context of their lives. The column is designed for curriculum enrichment, allowing the secondary schwl teacher to enhance the vitality of chemistry with the sense of scholarship and adventure shared by chemists throughout history.
in June 1912. Their children included a daughter, Margery, and two sons, Richard Newton and Edward Sheldon, both of whom pursued careers in chemistrv. t ~~aliforniaoffered Lewis a position In 1912, the l ~ n i v e r s iof as dean of a subdivision called the Collere of Chemistrv. The University Regents were intrigued hyuthe young physical chemist, less than 40, who had hecome acting director of research ,and a full professor a t MIT in such a short time. At Berkeley, Lewis made many costly and radical demands. He designed Gilman Hall primarily for research and the training of researchers. He established new re~uirementsfor the edication of hoth freshman and advaneed students. Special, diluted chemistni courses were abolished, and organic chemistry waseliminated from the homeeronomicsru~riculum. He appoint4 ulsther Hranch as the first womnn member of the chemistry fnculry at Herkeley. His goals were KIarouse the interest of the heginner, to give answers to queries on ~hilosoohiralimolications. and to nrovide methods for the investigator. He delineatedthese a i k in the introduction to his 1923 text, "Thermodynamics and the Free Energy of Chemical Substances," but feared that he had been overly ambitious in his attemots. Nonetheless. Lewis' colleee a t Berkeley became the woild's foremost center for teaching and research in ~ h v s i c achemistrv. l During orid id War I, Lewis was chief of the defense division as a lieutenant colonel in the Armv Chemical Warfare Service in France. He returned to ~ e r k e i e ya t the close of the war. Lewis presented his first paner on valence and electronic structure-in 1916 at the ~ r a i k l i nInstitute in Philadelphia. He based his theories on the octet concept and proceeded to develop a static model to illustrate the eight outer electrons. Lewis placed the electrons on the corner of a cuhe. All corners of the cuhe could he occupied hy the eight electrons of neon and other nohle gases. In the halogens, one corner was emptv: in the chalcogeni, two corners were unoccupied and so on the left of the periodic table where the alkali metals had hut one electron on one comer of the cuhe. Chemical combinations could he demonstrated by either transferring or sharing electrons and thus filling up the corners. In this elegant model, the concept of covalency was horn. The mechanism was an excellent technique for explaining the combination of metals with nonmetals and for demonstrating the stability of the nohle gas condition. I t called attention to the importance of the octet of outer electrons as a stable structure and to the value of the electron pair as a basis of bonding between atoms. "Valence and the Structure of Molecules," also published in 1923, developed a model for the molecular structure of compounds. Lewis produced the svmholism for electronic bonding in compouids which is well known to chemistry students. He let the ordinary svmhol of the element stand for the nucleus and all of the ele&ons except those of the outermost or valence shell. The outermost electrons were represented by dots. Hence, hoth bonding and structure could he implied. Indeed, this model also provided the foundation for the Lewis theory of acids and bases. Just as the Arrhenius paradigm did not support observations of acid-base behavior in nonaqueous systems, so too did the Br@nsted-Lowrymodel preclude an explanation of nonprotonated systems. Lewis' Volume 62
Number 7 July 1985
569
electron-based bonding and structure model logically addressed this impasse. A "Lewis acid" was defined as an ion or s molecule which can accommodate two electrons to complete its proper valence complement; thus, i t is an "electron-pair acceptor." The "electron-pair donor," which will provide the needed electrons t o the Lewis acid, is a molecule or ion with two uncombined electrons in the outermost shell. This is a "Lewis base." During the 1930'9, the development of the wave mechanical theorv of bondine bv Linus Paulina and others provided a physical basis foriewis' electronic models. The Lewis acid-base theorv. in 1923 hut not fully de.. suaaested -~ e l o p e duntil 1938, is yet a second fundamental principle of chemistrv which is exdained by those amazing electron dots. Lewis has been described as possessing a stimulating spirit of inquiry and engaging in intense scientific activity. He was able to maintain a unity of interest in prohlems and a cooperative approach w r
