The periodic table on tour.

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Eric R. Scerri travelled from the University of California at Los Angeles (UCLA) to the University of Calgary. The UCLA professor of chemistry and biochemistry was invited to speak at a conference of the International History, Philosophy, and Science Teaching Group on June 24, 2007. A special "author meets critics" plenary session was organized to discuss Scerri's book on the periodic table of the elements. This article will briefly examine the contents of the book and its implications for chemical education.

Scerri's book, The Periodic Table: Its Stow and Its Significance (Oxford University Press, 2007) is only the third comprehensive treatment to appear since the discovery of the periodic table in the 1860s. The first was F. P. Venable's The Development of the Periodic Law, published in 1896--before the discovery of the electron or modern theories such as quantum mechanics. Today's scientists may only find Venable's book to be of historical interest, but it does provide a compilation of early periodic systems.

After a gap of 73 years, the chemistry historian Jan W. van Spronsen published The Periodic System: The First Hundred Years. As the title suggests, its publication marked the 100th anniversary of the creation of the first mature periodic system by Dmitri Mendeleev in 1869. In terms of gathering a multitude of periodic tables and discussing their historical evolution, van Spronsen's book remains unsurpassed, although it has been out of print for many years. What van Spronsen's book does not provide is a philosophical account of the periodic system or an examination of its status in relationship to quantum mechanics. Given the role that modern physics has played in chemistry, this important omission motivated Scerri to write his book.

Scerri's book begins with an overview of the concept of an element, the discovery of the elements, their names, their symbols, and the major changes that have occurred to the periodic table. He examines the pre-history of periodic classification including the discovery of triads of elements such as chlorine, bromine, and iodine, and Prout's hypothesis whereby all the elements are regarded as composites of the lightest element hydrogen. Scerri continues with the work of Stanislao Cannizzaro who provided a set of consistent atomic weights in 1860. Those weights allowed a number of others to quickly assemble some early periodic systems.

Two entire chapters are devoted to the work of Mendeleev who Scerri describes as the champion of the periodic system in two senses. He is said to be the champion in the sense of having arrived at the first fully satisfactory periodic system and also as literally championing the system by making a number of successful predictions concerning as yet unknown elements.

Scerri's book turns to the discoveries in modern physics that were to have a big impact on the periodic system, while still leaving the system essentially intact. These developments include the discovery of the electron, atomic number, and the existence of isotopes of the elements. In the seventh chapter, Scerri provides a nuanced account of the work of physicists, in particular Niels Bohr and Wolfgang Pauli, who provided early theoretical accounts of chemical periodicity. According to Scerri, these accounts are not as deductive as generally implied in chemistry textbooks. This point has educational ramifications and Scerri returns to them in the remaining chapters of the book. Why teach chemistry as though it were nothing but quantum physics, he asks, since the reduction to quantum physics is incomplete? Why place such a premium on electronic configurations of atoms at the expense of teaching the chemistry of the macroscopic elements?

In Chapter 8, Scerri demonstrates that a number of physics-inclined chemists were able to deduce more accurate sets of electronic configurations than their physicist colleagues, simply because they had a more detailed knowledge of the chemistry of the elements. In Chapter 9, the attention turns to the impact of quantum mechanics as opposed to the old quantum theory of Bohr and Pauli. In the case of quantum mechanics, Scerri finds the reductive claim to be more plausible, although still incomplete. Nevertheless, Scerri is by no means opposed to the influx of physics into chemistry. He devotes a good part of Chapter 10 to an account of the evolution of the elements as revealed by modern astrophysics. Scerri ends the book by indulging in some speculations on whether there might be an "ultimate form" of the periodic table and discusses some leading candidates for this role.

This book will stimulate chemists, historians, philosophers, and chemical educators. Reviewers have described it as the definitive work in the field and a worthy successor to van Spronsen's work. The book also provides a fitting tribute to mark the 100th anniversary of the death of Mendeleev in 1907.