Chemical Education Today
Letters The “Dissing” of Niels Bohr In high school, students speak of being “dissed”, which can mean dismissed and discounted. In modern textbooks on general chemistry, for example (1), the contributions of Niels Bohr, except for his model of the hydrogen atom, have been discounted, and even the model is dismissed as being of value only for one electron species. By contrast, Sidgwick gave Bohr credit for recognizing in Thomsen’s periodic table the fruitful placing of the transition elements so that “a stable group has the form 2n2” (2). This contribution and Bohr’s authorship of the Aufbauprinzip (3) is not made clear in modern texts. Bohr arrived at his explanation of the Periodic Law by means of his correspondence principle (4). However, this principle cannot be employed in calculations (5). Accordingly, I believe, modern introductory texts only use quantum mechanics to explain energy sublevels. The idea of energy sublevels came from Bohr and Sommerfeld in response to the spectral line splitting observed by Zeeman and Stark (4). So, in an introductory chemistry course, I prefer to explain these sublevels by using Bohr’s approach rather than by detailing the “mathematical theory of quantum mechanics (which) is not suited to study by the beginning student” (6). Others too have found that “The old quantum theory of Bohr and Sommerfeld is still very useful from the didactic standpoint” (7). For an introductory course, I believe that before discussing quantum mechanics, the derivation of the Bohr theory
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of the hydrogen atom can be followed by presentation of the Stark and Zeeman results, which are available on the Internet (4). The students can then be guided to come up with their own correspondence principle leading, as it led Bohr, to the Aufbauprinzip. Literature Cited 1. Chang, R. Chemistry, 7th ed.; McGraw-Hill: New York, 2002; pp 252–273. 2. Sidgwick, N. V. The Electronic Theory of Valence; Oxford University Press: Oxford, 1927; pp 29, 41. 3. Bohr, N. The Theory of Spectra and Atomic Constitution; Cambridge University Press: Cambridge, 1922; pp 62–126. 4. Bohr, N. The Structure of the Atom. http://www.nobel.se/ physics/laureates/1922/bohr-lecture.pdf (accessed Oct 2003). 5. Kragh, H, In Niels Bohr; French, A. P.; Kennedy, P. J. Eds.; Harvard University Press: Cambridge, MA, 1985; pp 50– 67. 6. Pauling, L. College Chemistry, 3rd ed.; W. H. Freeman: San Francisco, 1964; p 197. 7. Persico, E. Fundamentals of Quantum Mechanics; Temmer, G. M. Ed.; Prentice Hall: New York, 1950, p vi. Andrew R. Peterson 8347 Grenoble Street, Apt. 3 Sunland, CA 91040
[email protected] Vol. 81 No. 1 January 2004
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Journal of Chemical Education
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