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Should Orbitals Be Taught In High School?
J. DUDLEY HERRON
Purdue Unwersily
West Lafayette, lndlana 47907
J a m e s J. Morwiek Oakwood Collegiate Institute 991 St. Clair Aue. W., Toronto, Ontario Canada M6E 1A3 The Arguments against Orbitals Some chemistry educators lament the fact that much theory has crept into introductory chemistry courses. Occupying a special niche as an offensive example is the quantum-mechanical model of atomic structure. The arguments presented against the inclusion of orbitals in high school chemistry are essentially two-fold. First, the concepts surrounding orbitals are so abstract and mathematical that many teachers do not understand what they are asked to teach. One critic asserts that the "SchrBdinger equation is produced "out of a hat" accompanied by some hand-waving about wave equations.. . and their solutions" ( I ) . He suggests that since students lack the background to understand mathematical solutions and quantum numbers, the whole subject of orbitals and hydridization is best left to a much later stage in the student's study of chemistry. Secondlv. the time soent on orbitals could be more fmitfullv spent on the "real" chemistry background needed by students. Topics such as the . omperties of non-metals and their im. portant compounds, mineral deposits, and pollution are sueeested. Some educators have become even more evanaelical on'ihis point; insisting that university chemistry enrollments are down because this "real" chemistry was not stressed snough in high school. Why the Critics are Wrong Let us examine these two points, one a t a time. First of all, science is a discipline that requires alot of abstract reasoning. This is a regrettable fact. Nevertheless, most high school students classify chemistry as a "hard subject" for this reason. Although a mathematical development of quantum mechanics and a solution to the Schrodinger equation is inaporonriate for an introductorv course. total disregard of the . modern notions of electron configuration is equally unacceptable. In fact, it is reasonable that a!omic structure and xbitals be taught a t a "hand-waving" level to senior high xhool students, particularly to those bound toward tertiary studies in science. Students can and should regard the atom as being composed of a dense, positively-charged nucleus surrounded by a cloud of negative electricity. In fact, students should be introduced to two possible ways of looking at this cloud of dectricity: one, as a distribution of electrical charge, over time, resulting from a negatively-charged particle (electron) moving about the nucleus in an indeterminate trajectory, or, two, as 3 "smear" of neeative charee that mav be thoueht of as being stationary (2)."The highscbool chemistry &dent is n; scarred for life if he or she nictures an "orbital" as beine this negatively-charged probability cloud. These images are not lust usrful: thrv are nn indis~ensibleintellectual wnftoldine upon which chemical bonding and molecular architecture can be depicted later. The debate over where the quantum model should be introduced boils down to the question of how it should be in-
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!62 1 Journal of Chemical Education
troduced. If one believes that the probability model of the electron should start with differential equations and normalized wave functions. then one is areuine- for introduction a t the university level. it certainlydoes not make sense to introduce it into high school in this manner. However, if one chooses to present the electron in the pictorial way outlined above, i t is possible to discuss i t in high school with senior students. In fact, students find science's inability to pin the electron down interesting, if not downright enchanting. They begin to see that science is not just a game where everything is all figured out. Furthermore, if the high school teacher can convey wonderment about this model of the atom, it can be discussed without stealing the thunder from the university course in chemistry, while creating anticipation for the mathematical hasis of this model. What Should Be Taught In hieh school. students should learn the shane of the reeion of space ~nccupied11). t~I~.ctr~m.i in rilrious t!nerm levels, and the\ shuuld be able todescrlhe the varinusenerrs levclsas I.,. 2s, i p and so forth. Studentsshould thinkof chemical bonding in terms of protruding "orbitals" overlapping to form a negatively-charged buffer zone between two positively-charged nuclei, and they should know that all forces related to chemical behavior are electrostatic in nature. However, students should not be expected to follow the mathematical arguments that lead to wive functions and to various quantum numbers, even though they should use the language . . and images of orbitals. Whether the high school chemistry teacher should get involved in topics s&h as hybridization, the imcertainty principle, or even antibonding orhitills depends OII the inwllectual curiosity of the studentscoucerned The Elusive Dreams of Unlversity Prolessors If I were a university professor, my life would undoubtedly be less comolicated if students arrived at the universitv unhlemished 6y misunderstandings and simplistic notions of what atoms are "really" like. Ideally, freshmen should be bubbling over with all sorts of interesting facts ("Silver cbloride is a white solid!") and all sorts of impatient auestions ("Why is silver chloride a white solid ratheithan a pale green aas?"). Accordine to this scenario. exoosure to factual chemistry would eventually result in an eagerness to learn about the theoretical model of atoms, bristling with all its thorny splendor. At this stage, the student could be taught the fullstrength, mathematical truth, unhampered by misleading m e n d images that succeed only in misguiding the student into thinking he knows far more about atomic structure than he actually does. Sounds convincing, doesn't it? There are two things about this notion that trouble me. Editor's Note: Recent plea; ft.r h1.h v h w d tmchrrqrl>rrdurt the:, trr.ttmcnt uf theory h a t e rrcnied rcmt'uswn and ,tmrrru 31x1111 just h w tar one nhuuld p,.1Ju we rl~mmntr0.1 rhrtq? I)II t r r i w o w i t w
disamee to Dresent oooosineviews. Contributions should be limited to f&, dau.ble-spacid,typewritten pages and should be sent to the column editor.
First of all, most students that I talk to are not nearly so compliant. They insist on didactic models as a lubricant for abstract topics such as atoms and chemical bonding. Educational research generally confirms this inconvenient fact. Whenever people are about to learn a particularly difficult concept, they usually revert toa method of reasoning (called "concrete operational" by Piaget) where easily visualized models are relied on heavily first ( 3 , 4 ) .Like it or not, the conjuring up of palpable images as an aid to understanding impenetrable mathematical concepts is a natural process that most people go through anyway. Secondly, I could never understand why a concept should he shelved until it is ready to he taught all a t once. In 1960, Bruner advocated a "spiral curriculum" approach in which quite sophisticated topics could be introduced in a preliminary, concrete way that is compatible with the students'mode of reasoning. Later, this same topic, anchored with some sort of reassuring physical model, could be approached in a more vigorous and abstract way. This seems a lot more sensible than the "all or nothing" technique. In this debate concerning theoretical chemistry in high school, there is a tendency to overestimate the benefits that accrue from "reintroducing" descriptive chemistry into the curriculum. According to this notion, the best students would he enticed into enrolling in chemistry courses a t college. No longer would adolescents he "turned off' by stale theories. Even if one allows for these hyperbolic dictums, one should not lose touch with reality. Adolescence can be a very turbulent time of life. Sometimes, teenagers are inclined to he a pulsating mass of misunderstood glands. Young people are not excited by a discussion of silver chloride, reducing agents, pollution, or, for that matter, orbitals. In short, they do not get excited by a curriculum, hut by teachers-math teachers and English teachers, as well as chemistry teachers. That does not mean that there are no interesting topics, hut it is ludicrous to pretend that an in-depth analysis of mineral deposits or more explosions in the laboratory will inevitably attract hordes of students to a serious study of chemistry. Nor should anyone be foolhardy enough to suggest that quantum mechanics be taught in high school to the exclusion of descriptive chemistry.
High school chemistry should be a general survey that ex poses students to a broad overview of the many different as pects of chemistry. One of the most fundamental aspectt happens to be quantum chemistry. I t is quite possible tha chemistry instructors (in high school as well as in university go overboard in teaching too much about orbitals too soon However, high school is no1 too soon to introduce a simplilied physical representation of the atom hired un thr quantum mechanicalmodel. The ohilosonhical controversv su&onndinr this depiction, and argkments'about what it ";eally" mean; can be postponed to some later stage of the student's educa tion. The idea that the evanescent, microcosmic world of na ture has an under~innina - based on ~robahilitvis one of t h ~ most intriguing revelations to come out of science. I t can, a n c should be introduced in high school even if only in an un complicated way. In fact, i t is this uncomplicated intrcductior that makes it possible to return to it later, and to study il again, abstractly and mathematically, in university. Literature Cited 111 (21 i:l) 141
Gil1espie.R. J., Chemislryin Conodo, 28.11, 23119'761. Monuick, J. J., J.CHEM.EDUC.,55.10,662 (19781. Herron. J. Dudley,d. CHEM. F.DUC.55.167. (1978). A ~ s ~ h pD. l .P . m d Robinsun. F. G.."Schml Leamine. An IntroductionToFdurationa
Errata The following references were omitted from the article in this column by Richard Jones, "A Formulations Lahoratory Project" [55,661 (1978)l. i l l Bennett, H. (Editor-in-ChWl. "The Chemical Formulary." Chemical Publishing Cu., Ine., Vol. 17, 1913. (Any vulume ithesetcontains many recipes and each vnlume is independent nii~therudumos.) 121 Stark,N.. "The Formula Manual." 3rd Ed.. Stark Research Cnrp~mation. Cedarhuw, Wl. 1975. I:ll "Honleyh Twentieth Century R9rmulas." lEdil
