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New Ideas in Chemistry from Fresh Energy for the Periodic Law by Henry A. Bent AuthorHouse: Bloomington, IN, 2006. 224 pp, ISBN 1425948626, $19.95 reviewed by A. Truman Schwartz
Henry Bent is and has been one of our most creative chemical educators. In 1965 he published The Second Law (1), a highly innovative introduction to classical and statistical thermodynamics. He pioneered the tangent-sphere model for molecular structure, chaired the ad hoc ACS committee that reviewed the numbering of columns in the periodic table, and did hundreds of demonstrations for schools and other groups from his mobile laboratory. Throughout his career, Henry has not been hesitant to express his sometimes iconoclastic opinions about chemistry and its teaching and to defend them vigorously. This book is a case in point. It is vintage Bent. The title pages disclose nine possible titles for what he calls his “report.” (The rather unwieldy title he did select is a reference to Mendeleev’s Faraday Lecture of 1889.) There are three abstracts of increasing length, 56 figures, 23 eclectic appendices, a synopsis, and a heavily annotated bibliography of 72 entries including those authored by Ludwig Wittgenstein, William Whewell, Dmitri Mendeleev (repeatedly), and many contemporary chemists. Henry has always communicated in aphorisms, and there is a nine-page list of aphorisms and summarizing statements. What is missing, unfortunately, is an index. The central thesis of the book, presented in 101 brief cross-referenced sections, is the chemical and pedagogical superiority of the left-step periodic table (LSPT). In this representation there are 32 columns and 8 rows. At the far right of the table are the first two columns, headed by H and He and eight elements high (the table goes to element number 120). Immediately to the left of this “s” block are the “p” elements, then the “d” elements, and at the far left and bottom of the table are the “f ” elements—the lanthanides and actinides. Atomic numbers increase regularly as one reads from left to right and top to bottom. In the left-to-right overall sequence, the orbitals “added to” are f, d, p, and s, hence the arrangement is also called an fdps table. Columns are labeled with Roman numerals representing the number of valence-shell electrons followed by f, d, p, or s. The LSPT has a number of attractive features. For one thing, it is beautifully ordered and aesthetically pleasing, though perhaps Bent places too much significance on what he calls the “Convention of Maximum Regularity.” It coincides with electronic configurations at least as well as any other arrangement, given the fact that the Aufbau is not quite regular. The table is
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gap-free and incorporates all the known elements without the need of putting the lanthanides and actinides in a “footnote.” Above all, Bent argues that the fdps system is the most “natural” arrangement of the elements. The author admits that the fdps arrangement also has weaknesses. Trends in elementary electronegativity, metallicnonmetallic properties, and the acid–base properties of oxides are not clearly revealed; and the placement of the alkali metals adjacent to the rare gases counters the familiar adjacency/ similarity rule. Bent argues that the virtues of the LSPT exceed these failings. But for many of his detractors, the necessity of placing helium above the alkaline earths is an irrefutable objection. Henry recognizes this criticism, indeed, he puns on his own name, Henry Bent, and returns repeatedly to justifying the placement of He above Be. He tells us 1s2 trumps inert gas properties, and placing helium among the alkaline earths is just the most extreme example of the distinctiveness of the first element in any family. According to Bent, Mendeleev himself would approve of this placement of helium. The father of the table made it clear that his classification was based on the properties of the abstract elementary entities that exist in all their chemical combinations (which Bent logically identifies with atoms), not just the properties of the pure elementary substances. The fact that in his later versions of the table, Mendeleev grouped helium with the other known rare gases is viewed as a temporary expedient. Of course Mendeleev did not talk very much about atoms; he could not have known much about them. But with a bit of historical hindsight, Bent reminds us that Mendeleev’s table was really based on atomic structure, whether he knew it or not. And furthermore, had he known about atomic spectra, atomic numbers, quantum mechanics, electron configurations, and the like, the great Russian would have favored the LSPT. Such groundless speculation strikes this reviewer as the weakest of the arguments advanced by the author. Bent cites more compelling evidence to support the LSPT and, in particular, the placement of helium. Unfortunately, after a time the references to dyads and triads, secondary and tertiary relationships, the special kinship of Mg and Zn, oxidation states, orbital energies, and the 11 integers of periodicity and their relationships become wearying. In short, the case is weakened by overkill. A more concise version would have been more convincing. Near the end of the book, on pp 191–192, there is a note added in proof—a letter from the author to Roald Hoffmann. It includes four statements about periodic tables:
1. No periodic table has all the desirable features periodic tables might have.
2. No periodic table is superior to all other periodic tables in all respects.
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3. No best periodic table exists, since the choice depends on use(s) to which the table is put.
4. Because the Periodic Law is one of the central doctrines of the Central Science, tabular expressions of it have many uses. There exist, consequently, many periodic tables.
I suspect that most chemists will agree with these very sensible statements. Yet, the fervor with which Bent advocates for the LSPT makes it clear where his allegiances lie (see especially Appendix XV). For 60 years, Henry Bent has been passionate in his advocacy, and that is key to his many contributions to chemical
education. This most recent contribution, controversial though it is, should be viewed in that light. Literature Cited 1. Bent, H. A. The Second Law: An Introduction to Classical and Statistical Thermodynamics; Oxford University Press: New York, 1965.
A. Truman Schwartz is an emeritus member of the Department of Chemistry, Macalester College, Saint Paul, MN 55105;
[email protected].
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