Eric Scerri

Most contemporary chemists consider quantum mechanics to be the foundational theory of their discipline, although few of the calculations that a strict reduction would seem to require have ever been produced. In this essay I discuss contemporary algebraic and diagrammatic representations of molecular systems derived from quantum mechanical models, specifically configuration interaction wavefunctions for ab initio calculations and molecular orbital energy diagrams. My aim is to suggest that recent dissatisfaction with reductive accounts of chemical theory may stem from both the inability of standard accounts of reduction to incorporate the diverse forms of representation found in chemical practice and our philosophical predilection to analyze all connections between theories in terms of logical reduction.

The main thrust of the paper involves a theoretical and philosophical analysis of the claim made in September 1999 that atomic orbitals have been directly imaged for the first time. After a brief account of the recent claims the paper reviews the development of the orbit and later orbital concepts and analyzes the theoretical status of atomic orbitals. The conclusion is that contrary to these claims, atomic orbitals have not in fact been observed. The non-referring nature of modern atomic orbitals is discussed in the context of Laudan's writings on realism, the success of theories, and whether or not scientific terms refer. I conclude that the failure to observe orbitals is a good prima facie case for divorcing the success of theories from the question of whether their central terms refer. The added relevance of this case is that it concerns a current and highly successful theory. Finally, the relevance of this ‘floating model’ to contemporary discussions on scientific models is briefly considered.

One of the consequences of the renewed interest in philosophical aspects of chemistry has been the corresponding renewed interest in the periodic system of the elements which embodies so much chemical knowledge in an implicit form.We have therefore decided to further promote scholarship on the periodic system by compiling a bibliography of previously published material. As the title of this article implies, we restrict ourselves to secondary sources. Readers interested in primary material can consult a number of useful references for this purpose. These include the classical treatment on the History of the periodic system by van Spronsen as well as Mazurs’s compilation of over 700 forms of the periodic system. Mazurs also includes a detailed bibliography of articles and books in several different languages. Additional sources of primary articles which come to mind include David Knight’s Classics in the History of Chemistry, Carmen Giunta’s web pages for the history of chemistry and entries under individual scientists in the Dictionary of Scientific Biography. Turning to the present compilation we do not claim this to be a comprehensive list, since it partly reflects the interests of the senior author (E.R.S.), namely the relationship between the periodic system and quantum mechanics. For example, in addition to articles specifically on the periodic system we include a number of articles which deal with the related themes of electronic configurations of the elements. This bias also explains the disproportionate number of references to the work of the senior author.We have tried to include as many as possible of the articles on the periodic system which have appeared in the philosophy of science literature. These include Bensaude, Christie, Hettema and Kuipers, Kultgen, Lipton, Maher, Scerri, Shapere and Sundaram, among others.

This issue begins the sixteenth year of our publication. It consists of the second part of the special issue dedicated to the late Richard Bader and edited by Cherif Matta one of his former students. For an extensive editorial covering the contents of both parts of the special issue readers should consult issue 3 of volume 15.C. Matta, Special issue: Philosophical aspects and implications of the quantum theory of atoms in molecules (QTAIM), Foundations of Chemistry, 15, 3, 245–251 (2013).I would like to mention two recent items that may be of interest to readers. The first is that Lee McIntyre and I have been asked by the publisher Springer to edit a second edition of our book that first appeared in 2005.The Philosophy of Chemistry: The Synthesis of a New Discipline, Baird, D., Scerri, E.R., McIntyre, L. (eds.), volume 242 of Boston Studies in the Philosophy of Science, Springer, Heidelberg, 2005. The new edition is almost ready and contains contributions from many well-known philosoph