Complete reviews of Eric Scerri's new book
elemental Deductions
Review by Seymour Mauskopf,
American Scientist
Eric Scerri's new book is a most appropriate work to mark the centenary of the death of Dimitri Mendeleev. The title - The Periodic Table: Its Story and Its Significance - gives a fair idea of the book's contents, and the author's approach and perspective are captured by his statement that he is concentrating on "the fundamental scientific and philosophical ideas that underpinned the evolution of the system." This, then, is a book about scientific ideas. Scerri does provide brief biographical sketches of each of his scientific protagonists, but biographical, social and cultural context rarely intrude into the narrative.
A number of philosophical and historical concepts govern the narrative in the first half of the book, which covers the history of classification of the elements up through the development and reception of Mendeleev's periodic system. Scerri makes the point that Mendeleev's achievement was not a paradigm shift but a more gradual evolution, spanning much of the 19th century and picking up momentum in the 1860s in the wake of the clarification of atomic weights by Stanislao Cannizzaro. Indeed, Scerri goes so far as to characterize the history of the periodic system as "the supreme counter_example to Thomas Kuhn's thesis, whereby scientific developments proceed in a sudden, revolutionary fashion."
Another premise set forth is that scientific "mistakes" sometimes have good results and inspire creative thinking. The most important example Scerri gives of this process is the influence of William Prout's hypothesis that all atomic weights are integral multiples of hydrogen. Some philosophers in ancient Greece believed that an underlying primary form of matter, which they named protyle, was the basis of all matter, and Prout theorized in 1816 that hydrogen was it and thus underlay all apparent elemental diversity. This theory, although dismissed and "disproved" in the mid-19th century, led many scientists to look for relations between groups of elements based on atomic weight and chemistry. The notion that "mistaken" scientific ideas can play a positive role is nothing new to historians but may be more provocative to philosophers of science and scientists.
Analyzing the concept of an element, Scerri identifies three subcategories: property-bearing abstract elements (such as Aristotle's fire, earth, water and air); simple substances (the empirically defined elements of Lavoisian chemistry, which cannot be decomposed by any known means); and the material ingredients of substances (those which participate and persevere in a chemical compound). For Mendeleev, it was the abstract element-now with the sole discernible and measurable property of atomic weight-that persevered in a chemical compound. Thus Scerri argues that atomic weight became the preeminent characteristic of chemical elements for Mendeleev. (Later in the book, Scerri employs the phrase basic substance to further differentiate between Mendeleev's elements, which were defined by atomic weight, and 20th-century elements, which are defined by atomic number.) This is an extremely interesting philosophical analysis, one that would have benefited from additional historical context.
Scerri argues that Mendeleev's periodic system was accepted primarily because it had the characteristic of "accommodation," by which he means "the ability of a new scientific theory to explain already known facts."He contrasts this with the more widely held view that it was Mendeleev's dramatically successful predictions of new elements and their properties that won the day for his system. Indeed, Scerri takes on recent assertions by two philosophers of science on just this point. Yet he provides almost no concrete historical evidence to support his contention-which is a shame, because the issue of what led to the acceptance of this comprehensive chemical system invites comparison with its nearly contemporary biological analogue: the reception accorded to Darwin's theory of evolution by natural selection.
In the second half of the book, Scerri turns to developments in physics early in the 20th century that are often taken as providing the theoretical basis for the periodic ordering of the chemical elements. These include the discovery of the electron, the delineation of a "solar system" model of the atom and its quantization by Niels Bohr, the enunciation of the concept of the isotope, and the recognition that elements are defined (and differentiated from one another) by atomic number (eventually identified as the number of protons in the atomic nucleus) rather than by atomic weight.
By 1920, Bohr and his colleagues had devised models of atoms comprised of nuclei surrounded by multishelled electronic configurations. These models offered insightful, although incomplete, theoretical explanations for the periodic relationships between the elements. Soon the development of quantum mechanics provided refinements to and extensions of the explanatory power of quantum physics.
Indeed, as Scerri notes, one of the principal architects of quantum mechanics, Paul Dirac, declared in 1929 that "The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known" (emphasis mine).Dirac's dictum could serve as something of an epigraph for the second half of the book, which I found more enthralling than the first half's description of the development of the periodic system.
Scerri's persona as a philosopher of chemistry really comes into its own in the later chapters. The main thrust of his argument is to counter the deductive and "reductive" (to use his word) dicta espoused by physicists such as Dirac and by many authors of chemical textbooks. Although Scerri is not as explicit as he might be, he is attempting to show that chemistry, particularly as embodied in the periodic system, is profoundly different from physics and in particular is resistant to the kind of deductive generalities that physics offers. For at least 300 years (since the criticism of Bernard de Fontenelle in 1699 that, compared with physics, "the spirit of chemistry is more confused, more shrouded"), chemists have often suffered from a sense of scientific inferiority and consequently have felt the need to legitimate their science using the theoretical basis of physics.
Without denying that 20th-century quantum mechanics has provided a great deal of theoretical insight for the periodic system, Scerri champions chemistry as a science in its own right-a richly empirical one that deals with the material world in all of its variety and complexity. Behind this effort lies a didactic purpose. Scerri notes that most textbooks imply that quantum mechanics satisfactorily explains the periodic system. This, in turn, fuels the general impression that chemistry is fully explained by quantum physics and has a negative effect on chemical education. Instead of starting from chemical facts, and the properties of the elements, the modern tendency is to expose students to the rules for electronic configurations in the belief that the chemistry will somehow follow.
Presumably as a corrective, Scerri provides a most interesting chapter on periodic systems that chemists have constructed in the 20th century with little or no reference to quantum theory or quantum mechanics. A chapter on the complex relation between quantum mechanics and the explanation of chemical periodicity follows, providing many anomalies that complicate a straightforward reduction. Indeed, Scerri characterizes the explanatory success of quantum mechanics for the periodic table as "something of a miracle." But he concludes his book with a positive nod to physics in a chapter on astrophysical theories of nucleosynthesis.
The classic predecessor of The Periodic Table is J. W. van Spronsen's 1969 book The Periodic System of Chemical Elements: A History of the First Hundred Years. The material covered is quite similar, but van Spronsen's account, much more iterative than Scerri's, provides more examples of the great diversity of periodic systems that have been constructed, particularly in the 20th century. Scerri, by contrast, is much more attuned to the kind of philosophical issues outlined above, and he gives a much deeper and more comprehensive study of the developments of 20th-century atomic physics and quantum mechanics.
The Periodic Table is written in a straightforward style. However, Scerri has an annoying tendency to extol his own virtue in uncovering hitherto ignored historical personages and data. Another minor caveat is that the name of the very important 19th-century French chemist Jean-Baptiste-André Dumas, although given correctly on first reference, is twice mis-styled in the text as "Alexandre Dumas" and appears in the index as "Dumas, André."
Notwithstanding these imperfections, this book is a fine addition to the history and philosophy of chemistry, fields that Scerri himself has played an important role in developing.
THe PERIODIC TABLE
Its Story and Its Significance
Review by John emsley,
Times Literary Supplement
In 2006, the Royal Institution declared Primo Levi's The Periodic Table the best science book ever written. Its title, however, is misleading because it is not about the periodic table of the chemical elements, though each one of its tywenty-one chapters is named after one. (It is the autobiography of a chemist who survived Auschwitz.) Eric R. Scerri's The Periodic Table, on the other hand, does exactly what one might expect.
Hundreds of periodic tables, of all shapes and sizes, have been devised down the years. Not only does this icon of chemistry adorn schoolrooms and college lecture theatres, it is now found on mugs, ties and beer mats, and in car advertisements. Strangely, relatively few books have been devoted to it, which makes Scerri's particularly welcome - all the more since not only does he recount events leading up to its discovery, but also analyzes its underlying meaning and implications.
It is an urban myth that the the Periodic Table came to an obscure Russian chemist, Dimitri Mendelev, in a dream in 1869. Like others before him, Mendeleyev was musing on why there were so many elements -- he knew of sixty-five, we know of 115 -- and how some could be grouped together on the basis of shared properties. By this time their atomic weights were accurately known and what Mendeleyev did was to arrange the elements in order in rows and columns. He then noticed gaps in his table, so predicted the existence of the missing elements and forecast their chemical behaviour. In several cases, his predictions were spot on.
The second half of the Periodic Table may prove demanding for the general reader as it delves with the structure of atoms, their electronic make-up, and the role of quantum mechanics. Most appealing about this part of the book is Scerri's philosophical musing on the status of chemistry and his conclusion that it is not merely, as some theorists would have us believe, an adjunct of physics.
March 16, 2007
THe PERIODIC TABLE
Its Story and Its Significance
Review by A. Truman Schwartz,
Macalester College, St. Paul, MN,
Journal of Chemical education
Eric Scerri is something of a rara avis. He appears to be well informed about descriptive inorganic chemistry and quantum mechanics, he exhibits considerable knowledge concerning the history of chemistry, and he is one of the most prolific practitioners of the new field of philosophy of chemistry. His interest and experience are evident in this admirable study of the icon that encapsulates chemistry-the periodic table.
After a brief introduction, Scerri provides (in Chapter 1) an overview of the periodic system and the book. Chapters 2 through 5 are primarily historical. They describe early attempts to organize and classify the elements on the basis of their chemical properties, the co-discovery of the periodic law, the special contributions of D. I. Mendeleev and the reception of his system and table. Much of this material has already been addressed by van Spronsen (1), but in the last half of this book Scerri goes well beyond the Dutch author's classic work. Chapter 6 discusses the impact of discoveries such as radioactivity, atomic number, and isotopy on the periodic table; and Chapters 7, 8, and 9 introduce electrons, electronic configuration, and quantum mechanics. The final chapter is a bit of a grab bag, with sections on astrophysics, nucleosynthesis, periodic trends, and complicating details such as diagonal effects, secondary periodicity, the knight's move relationship, and first member anomalies.
Scerri's philosophical orientation enriches the text by raising a number of thought-provoking issues. For example, he argues that the development of the periodic table is an evolution of scientific ideas, not a scientific revolution in the Kuhnian sense. To be sure, Mendeleev deserves his well-established place as "the undisputed champion of the periodic system", but he was undoubtedly influenced by the work of others. Scerri credits De Chancourtois, Newlands, Odling, Hinrichs, and Lothar Meyer as having made significant contributions. The triumph of Mendeleev's system is often attributed to his accurate predictions of the properties of three undiscovered elements-scandium, gallium, and germanium. But Scerri points out that an equal number of the great Russian's predictions proved to be wrong. He uses this to help support the thesis that the accommodation of known and subsequently new facts was more important than prediction in the acceptance of the periodic law.
Mendeleev made a distinction between elements as common "simple substances" such as the liquid metal we call mercury and more abstract metaphysical entities that somehow retain their identities in chemical reactions. The periodic classification was originally based on the latter concept, not the former. Scerri's argument that this distinction is still a useful one convinced this reviewer. However, I wish he did not refer to abstract elements as "basic substances". The specific chemical meaning of "basic" introduces possible confusion. "Fundamental" or "essential" would be more appropriate modifiers.
In this book, and some of his other writings, Scerri is much concerned with whether chemistry can be reduced to physics. In 1929, the theoretical physicist Paul Dirac famously declared: "The underlying laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known." The only difficulty seems to be in applying the laws and doing the math. Scerri regards the periodic table as "a test case for the adequacy of the new methods developed in quantum chemistry". While granting the insights to periodicity provided by electron configurations, Scerri points out that the order of shell filling has not been deduced from first principles. Quantum numbers preceded quantum mechanics, the Pauli exclusion principle and Hund's law are empirically based, and ab initio calculations are still guided by semi-empirical considerations. As someone first attracted to chemistry by sights, smells, and sounds, I would not be disappointed if Dirac's dream remained forever unrealized.
The book ends with a question that many chemists are inclined to dismiss: "Is there one most fundamental periodic table?" e. Z. Mazurs's exhaustive study (2) analyzes 700 versions and reproduces many of them. Scerri grants that various versions of the table emphasize different aspects of periodicity and serve different pedagogical purposes. However, he suggests that the left-step or Janet arrangement, based on the n + l sum of quantum numbers, best reflects chemical periodicity. This is the same form advocated by Henry Bent in his recent book (3). I am not entirely convinced, and not just because it makes bedfellows of helium and beryllium. But certainly the left-step version deserves a place at the table.
The book under review here is clearly and engagingly written and meticulously researched with 42 pages of notes. The work is nicely illustrated with photographs, tables and graphs of data and various versions of the periodic table. Many are reproduced from original sources
The Periodic Table: Its Story and Its Significance should be of great interest and value to chemists and particularly to those chemists who teach about the stuff that makes up us, our world, and our science. It is instructive that Scerri, in his introduction, identifies chemical periodicity and chemical bonding as the two big ideas in chemistry. It is equally instructive that we cannot offer definitive and complete explanations of either subject. So we continue to tell our students useful and sometimes contradictory semi-fictions about our big ideas. This book will make our declarations better informed.
Complete reviews of Eric Scerri's new book