provocative opinion Is the Theoretical Emperor Really Wearing Any Clothes? R. T. Sanderson' Arizona State University, Tempe. AZ 85281
As our knowledge of chemistry continues t o explode, the unity of this vital science becomes more and more dependent on fundamental prinriples of atomic structure and chemical bonding to preserve its integrity. But these must be thoroughly and continuously related t o practical chemistry or thev lose their nower and their unioue value. Out of this now almost infiniteLfieldof knowledge, what do we hope to teach? We certainly cannot wish t o waste time on material that accomplishes little toward the chemical education of our students. Nor should we wish to omit material that can he uniquely and genuinely helpful. I am writing this because I think general practice is to do both-push forward material of very doubtful value except p o s s i b l G avery small minority and omit material that could be very useful to all. I urge all who have an interest in the effective teaching of chemistry, and especially of general and inorganic chemistry, to take along, fresh look a t what conventional theory has to offer toward an understanding of commonplace and relatively simple chemistry. One can study electronic configurations, molecular symmetry, and group theory, learn how to determine the relative ~ercentaeesof s and D orbitals alleeed to he involvnd in a given bonding situation, write wave equations for each orhitnl and draw imoressive molecular orbital energy diagrams, and provide complex mathematical description of a molecule, but what can these teach about chemical bonding? Look a t any hook on chemical bonding (except my own), or any discussion of chemical bonds in any textbookor treatiseofphysical rhemistry,crrany t ~ x r b o o k ~ f inorganic or general chemistry and you will find almont nothing to provide a practical understanding of why atoms combine in the way they do, where the energy of their combination originates, why certain types of bonds seem favored over others, why some bonds are stronger than others, and. in eeneral. whvchemical reactions occur and whv the products are favored over the reactants. The beautifil cause-and-effect relationship between the structure of atoms and the properties of their compounds is hardly considered and certainly not clearly revealed. If the thoughtful reader really believes that theoretical chemistry has provided much help in understanding that most fundamental concept, the chemical bond, then I suspect it is because we have all been so brainwashed into believing that the Schrodinger equation is the complete guide to chemical understanding that we have not dared to examine other possibilities. But that's only a suspicion. I don't know the explanation. Far be it from me, a nonpractitioner. to admonish the theoreticians. Thev are demonstrably more capable than I, and they are directing their talents toward proeress in an extremelv difficult and comolex field. Most of them deserve and receive our respect a n i admiration. Less than admirable, however, is their oroven eaeerness, and that of their uncritical followers, to censor alternative simpler ideas that aremore successful, to the extent that almost the only way t o publish less conventional ideas is to
-
write another book. I suspect they tend to judge such work by their own strange standards: (1) if the idea is simple enough to be understood, i t cannot possibly he correct, and (2) if i t consistently produces quakitatively accurate results, this must be entirely fortuitous because obviouslv it neglects so many important essentials that there is-no chance of accuracy except by the purest of luck. The fact as I view it is that a very useful approach to understanding fundamental chemistry that could be extremely and uniquely helpful to students is deliberately being kept from them. Why? I have been unable to discover. I find it im~ossibleto imaeine an aoorooriate .. . excuse for textbooks purporting to becomprehensive to be so deficient. Their readers will learn the erroneous Pauline derivation of electronegativity hut not more accurate metlhods, and will study Paulinp's electroneutralitv principle but never be told of the of e ~ e c t r o n e ~ a i i h equalization ty (now for nearly a decade approved by experts in quantum mechanics). They will read about how difficult it is to measure atomic charge but receive no hint that such charees have been easily available for 32 years and are uniquely Gseful in the interpretation of much of inorganic chemistry and indispensable in the accurate calculation of energies of thousands of polar honds. They will learn that repulsions between lone pair electrons on the adiacent atoms cause weakenine of &ngle N-N, 0-0,and F- bonds, although this effect (wkch is also significant for the heavier elements of these erouns. a fact never mentioned) has been known for a t least l j y e a k t o be within each atom hearing lone pair electrons, n o t between atoms. They will learn to use heats of formation with no suggestion that thev are reasonable conseauences of easily und&tandal)lc atomic properties and ranbiten be calculated from rhem. They will be provided with a table of bond energies with no hint that these can he calculated accurately from a simple quantitative theow of polar covalence that reveals the origin of those energies, aiailahle for 20 years. They will he shown the details of the "ionic model" without beingtold how more accurate calculations result from taking into account the considerable covalent character of all binaN com~ounds.Nowhere will thev learn whv air isn't solid. why carbon dioxide and sand arebo different, why oxides of nitrogen are unlike oxides of heavier elements of the eroun. etc. F'inally, they will no doubt be deeply puzzled the overwhelming.. implication that wave eauations and molecu. lar orhiral diagrams are theexplwati;n of rhemical bonds. 1\11this help and much more that could br vrrv beneficial to students a i d to chemists in general is bidden from them, for reasons that seem to defy logical explanation. I t has long seemed to me chat, in nature, beautiful simplicities are blended with infinite complexities. The ultimate truth is probably forever unattainable, but the beautiful simplicities can be recognized and used effectively to create
cy
'Present address: 4725 Player hive, FORCollins, CO 80525. Volume 63 Number 10 October 1986
845
the illusion of understanding. This is not to deny the merit of studying the complexities with all possible intellectual talent. But there is nothing wrong with the simplicities, either, as long as they can he perceived correctly and used with a clear understanding of what they are. I believe it is unfair to our students to deny them an opportunity to appreciate the simplicities, for acquiring a practical understanding seems far more helpful than being confronted with complexity beyond real comprehension. I have never been persuaded that ignorance gains preferred status by being pursued a t a
848
Journal of Chemical Education
higher level of sophistication-it is ultimately ignorance all the same. I t is very difficult for me to understand how so many teachers of chemistry can so meekly and unquestioningly admire the theoretical emperor's beautiful new suit of clothes when in fact he is standing there practically stark naked. Well, maybe he is protected a little by equations that can never be solved and hy molecular orbital diagrams that keep his electrons sorted out. But for his sake, I hope it isn't very cold where he is standing.
