JOSEPH S. SCHMUCKLER Chalrman of Sclence Education Temple Unwersity 345 Rmer Hall Philadelph~a,PA 19122
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Bonding, Structure, and Geometry 1 ) "Simple Two-Dimensional Magnetic Disc Models of Ionic Liquids" C.A. Augell, D.M. Gruen, J. CHEM. EDUC.,43, [4], 1 9 4 (April 1966). Physical models can give insights about processes occurring in different forms of matter. The authors present two models capable of showing to first approximations nearest neighbor interactions of floated "ion" magnets on water. A radially uniform magnetic field in the horizontal plane is obtained by wrapping a Plastiformstrip around the outside of a 6-in. Petri dish. The "ions," disn of plastic magnetized sheets, are cut and fastened onto dises of cork.The experimenter can observe chanees from one svmmetrical form to another as more "ions" are added. .&me insight ktodetailvofthe meehnnismof the rr& tonnation can be gained by uherving . . . a configu~a~ion of maximum energy ("aetwwd eumpler?"~befire an additional "ligand" heromes bound and the resultant symmetrical configuration becomes energetically favored." The second model achieves stronger interactions. Phenomenasuch as "free volume," tetrahedral and octahedral arrangements can be achieved. Some ideas of diffusion can be obtained as well as "crystallization." The addition of neutral discs can show the effect of "charge density" on miscibility. l'heauthom present enoughdiagmtns and pictures that can assist the reader tu duplicate their work with some degree of ease. ~~
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2) "Chemical Geometry-Application to Salts," Thomas R.P. Gibbs, Jr., and Anne Winnerman, J. CHEM. EDUC., 35, [lo], 578 (November 1958). In the authors own words: "Crystallography is a topic which frequently excites the interest of the elementary student, hut as is so often the case, the typical texthook treatment is not deep enoughto develon or sustain this interest. The outward form of m t d s no loneer has thr malor significance it did in the day* of past&. nor ran any rcnlly satisfying treatment be given crystal morphology in an elementary chemistry course: studenw are "let down" when they find that one cannot tell the crystal system by lwking at the crystal, On the other hand, the inward structure of crystals can he made a very rewarding part of the classical course, and particularly of a course devoted to the chemical bond. I t is the purpose of this article and a succeedine " one to illustrate how one mav delve rather deeolv intu noma nsprcts of rrystal structure which are of special interest chemically, without h m i n g involved in the symlmlog.andsemantic rmnplexlties of ronventional crystallography. r\ further purpose is to show how elementary mathematics is a powerful tool of the chemist and to indicate areas of chemistry which offer a challenge to the better student's creative potential. I t is the author's conviction that the objectives cited in the preceding sentence are enormously more important in an elementary course than purely descriptive material. Why lithium fluoride is unlike the other alkali metal fluorides is certainly mare interesting than the mere fact of its insolubility in water."
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3) "Foundations of t h e Structural Theory," H e r b e r t C. Hrown, J. C H E M . EDUC., 36,[3],104 (March 1958). Brown's paper was presented in honor of the KekuM-Couper Centennial. Brown's remarks of 1958 still hold. "Little attention is
810 I Journal of Chemical Education
paid to the history of chemistry in our schools today."". .we discthe chemistryof hundreds of thousands of organic molecules in terms of their structures. We interpret the behaviors of high polymers in terms of their molecular constitution and coniiguration. We interpret the hehaviors of drugs in terms of their molecular dimensions and shapes and their abilities to occupy molecular sites of related shape requirements in biological systems. Finally, we are making active progress in unraveling the structures of those amazing versatile nolvmers of life-the nroteins. . . "Onp hundred year* of atrueture-one hundred years of amazing progress! We owe a real debt ctf gratitude to the two young chemists whu first pointed the way to this ma~nificenthighway of rhemiral investigation. I t is fitting that we commemorate their contribution and honor their memory."
4) "Principles of Chemical Bonding" R.T. Sanderson, J. C H E M . EDUC., 38, [8], 382 (August 1961). R. T. Sanderson perhaps more than most authors of these current times has been one of the more prolific writers who attempts to put chemical theory into meaningful words and physical models. Accordingly he sap, "An understanding of chemical bonds is so essential to a true appreciation of chemistrythat simple yet reasonable valid explanations must be continuously sought and improved." Starting with a definition of a chemical bond, the author treats the subject". . .through consecutive consideration(s) of a set of principles." Sanderson writes well for teachers of beginning students in chemistry. For those who want andlor need a review of principles of chemical bonding, this article is a superb reference.
5) "Some Reflections on the Use and Abuse of Molecular Models," Quentin R. Peterson, J. C H E M . EDUC., 47, [I], 24 (January 1970). "To some teachers an atom is always a hall. In winter, it's a hssk e t h d , in spring it's a basehall, and the rest of the time it's a pingpong hall. The atom is no more explained by such images than the idea of God is a picture of an old man with a Long heard sitting on acloud." Throughout his paper, Peterson develops historically various models put forth by earlier investigators and the criticisms they endured. The article ends with a long excellent quote made by Langmuir in his pres;dential address to the Ameriean Chemical Society, part of which is printed here: "Skeuticism in regard t o a n absolute meanine~,of words. eoneents. model* or mathematical theories should not prevent us frum using all these abstrartimr in descrihmg natural phenomena.. . We must recognize, however, that all of these concepts are human inventions and have no absolute independent existence in nature." ~
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Annotations of artides from previous issues of the JOURNAL, dating back as early as the 1950'8, are included in this monthly feature. Topics will be presented one month prior to their scheduled time to he taught in the typical high school curriculum.
