DISCUSSION OF THE PAPER

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DISCUSSION OF THE PAPER W. ALBERT NOYES, Jr. University of Rochester, Rochester, Nau York

THOSE teachine.. nhvsical chemistrv are Dresented with a real . . dilemma, sinre the majority of underfladuatrs will find placer in the industry without prwreding to r a d u a t e s h w l s The course must, therefore, be designed to meet the needs of these as well u of the relatively few who do go on to graduate work, and of the minute number who intend eventually t o specialize in the more purely scientific aspects of physical chemistry. In large institutions classes might well be divided into sections dependent upon ability and inclination, hut in the smaller institutions this cannot be done without making sections so small as t o be impracticable. A course in physical chemistry must, therefore, include a rather strong emphasis on what might be termed the classical branches of the subject. Nevertheless, we must be milling to introduce theoretical matter which aids in correlating different phases of the subject. This means t h a t if the introduction of wave mechanics will permit the average student to appreciate interrelationships between various fields i t is highly desirable. As Professor Glockler has oointed out. i t is necessarv t o have same undcrstnnding of wave merhanir, in u r d u to appreciat~ modern theoried of wlency und of chemical binding. 1:rorn the course in physics the .tudent usually remembers that the vihrating string and certain other physical phenomena can be treated with the use of differential equations and that certain wholenumber relationships usually appear when wave equations are used. I t seems to me, however, t h a t it is vitally important t o i n t r u dnce the student t o the nhvsical reasons whv whole-number relationahips and quantum descriptions are necessary in dcaling with certain atomic and molecular phenomena. Before o m givcs ~~~~

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anv solutions of wave eauations the student should have a thoro~lahfamilvnrity with certain simple facts of spectroscopy, of specific ht;,ts, of reaction rates, of the p h ~ t ~ l e c t rcffcct, ic and of certain other subjects which demand quantum explanations. The average junior in a n American university is usually completely lacking in the experimental background which is necessary to comprehend the reasons for introducing wave mechanics. I t is perhaps not worth while to indulge in a detailed treatment of the Bohr atom. It mieht he described and the obiections t o it pointed o ~ l t Indced, Lwicf introduction of the Heisenberg unwrtaints principle would help the student to aprmciote the dillculliec in inela*tic atom models. The descriptions of valence forces in terms of exchange and coulombic binding and of resonance scarcely demand any solution of wave equations, but will help the student t o appreciate the difference in point of view between clwical and atomic systems. I n some ways i t would be mare useful t o introduce the students in elementarv cbemistnr to the foundations of statistics . .Dhvsical . than to detailed solutions of wave equations. Cse of statictic- is hcruming well-nigh universal in the trtstment of chcmical prohIemq and will in n o way depend on a n y particulnr atom nmlel or system which is used to describe energy states of atoms and molecules. Thus, while we might agree in the main with the thesis of Professor Glackler t h a t very new developments should be introduced into elementary physical chemistry courses, we must emphasize t h a t it is more important a t that stage of the game t o develop a real appreciation and feel for physical phenomena than i t is to introduce rigorous mathematics.

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