The periodic table of the elements is one of the most powerful icons in science: a single document that captures the essence of chemistry in an elegant pattern. Indeed, nothing quite like it exists in biology or physics, or any other branch of science, for that matter. One sees periodic tables everywhere: in industrial labs, workshops, academic labs, and of course, lecture halls. It is sometimes said that chemistry has no deep ideas, unlike physics, which can boast (...) quantum mechanics and relativity, and biology, which has produced the theory of evolution. This view is mistaken, however, since there are in fact two big ideas in chemistry. They are chemical periodicity and chemical bonding, and they are deeply interconnected. The observation that certain elements prefer to combine with specific kinds of elements prompted early chemists to classify the elements in tables of chemical affinity. Later these tables would lead, somewhat indirectly, to the discovery of the periodic system, perhaps the biggest idea in the whole of chemistry. Indeed, periodic tables arose partly through the attempts by Dimitri Mendeleev and numerous others to make sense of the way in which particular elements enter into chemical bonding. (shrink)

The periodic table may be seen as the most successful example of inquiry in the history of science, both in terms of practical application and theoretic understanding. As such, it serves as a model for truth as it emerges from inquiry. This paper offers a sketch of a central moment in the history of chemistry that illustrates an intuitive metamathematical construction, a model of emerging truth. The MET, reflecting the structure the surrounds the periodic table, attempts (...) to capture the salient epistemological elements that warrant truth claims based on sets of models that are progressive in light of both empirical and theoretical advance seen over time. (shrink)

The philosopher of chemistry Andrea Woody has recently published a wide-ranging article concerning the turn to practice in the philosophy of science. Her primary example consists of the use of different forms of representations by Lothar Meyer and Mendeleev when they presented their views on chemical periodicity. Woody believes that this distinction can cast light on various issues including why Mendeleev was able to make predictions while Meyer was not. Secondly, she claims that it can clarify the much-debated question concerning (...) the relative values of prediction and accommodation of data in the way that the periodic system was accepted. Thirdly, Woody believes that such differences in the representation of periodicity can be used to argue for the explanatory nature of the periodic table in contrast with the more traditional view that the periodic table is not explanatory. (shrink)

In this essay, we aim to provide an overview of the periodic table’s origins and history, and of the elements which conspired to make it chemistry’s most recognisable icon. We pay attention to Mendeleev’s role in the development of a system for organising the elements and chemical knowledge while facilitating the teaching of chemistry. We look at how the reception of the table in different chemical communities was dependent on the local scientific, cultural and political context, but (...) argue that its eventual universal acceptance is due to its unique ability to accommodate possessed knowledge while enabling novel predictions. Furthermore, we argue that its capacity to unify apparently disconnected phenomena under a simple framework facilitates our understanding of periodicity, making the table an icon of aesthetic value, and an object of philosophical inquiry. Finally, we briefly explore the table’s iconicity throughout its representations in pop art and science fiction. (shrink)

In case of that human civilization was viewed as an integrated organism, the Periodic Table of the Civilizations (PTOC in short) has been formulated and recommended based on the development level and periodicity of core elements of human civilization. It divides the frontier process of the human civilization from the birth of humankind to the end of twenty-first century into 4 periods and 16 stages, and in which four periods include that of primitive culture, agricultural civilization, industrial civilization (...) and knowledge civilization orderly, and each period includes four stages, that is, start, developing, maturing and transition stages sequentially. There are three approaches for the arrangements of the PTOC, that is, simple, vertical and horizontal tables. The big period of earth civilization refers to that from the primitive culture to the knowledge civilization, and then big period of space civilization will begin with the astronautic civilization. The first modernization witnesses the great changes and transformation from the traditional agricultural to the modern industrial civilization, and then second modernization from the modern industrial to the higher modern knowledge civilization. The periodic table, coordinate system and roadmap of human civilization and world modernization have been formulated to describe the relationship between them. (shrink)

This manuscript aims to systematically consider the main periodicity and additional (secondary, internal, and tetrad) periodicities using a uniform approach. The main features are summarized in table form. The history of the origin and development of these concepts is discussed. It is described how these periodicities manifest themselves and how they are determined at the experimental and theoretical levels. Areas of manifestation of these periodicities are outlined. As the general approach to explaining internal periodicity, attention is drawn to the (...) symmetry of the quantum number S of atoms and the principle of equivalence of electrons and holes. Arguments are presented in favor of a more correct classification of the tetrad effect as tetrad periodicity, and an overview of this regularity is provided. A small modification of the conventional Periodic table is proposed, which reflects all the mentioned periodicities. (shrink)

The concept of major scientific advances occurring as a short-term ‘revolutionary’ change in thinking interspersed by long periods of so-called ‘normal’ science seems to be losing ground to more ecological models, which are more inimical of the twists and turns of life. From this idea it is a short step to charting science’s progress against stages used in fictional storytelling, which after all is life-based. This paper explores the development of the periodic table in terms of the achievement (...) of a fictional ‘quest’, and finds the stages of such a story are well represented. While Mendeleev or perhaps Meyer might be considered by some to be the hero of the quest, its first stage—the call—is represented by the Karlsruhe conference in 1860, with an international cast of ‘companions’ and ‘helpers’ who contributed to the Table’s early development. The ‘journey’ may have been frustrated by lack of appropriate data and understanding of concepts, but the ‘arrival’ phase is clearly marked by the award of the Davy medal jointly to Mendeleev and Meyer in 1882, Throughout these stages there are lesser, although still significant contributions made by “little people” of science to the overall progress of the Table. The end of the journey is not the end of the quest: the discovery of new elements—“new ordeals”—and their incorporation into an increasing range of types and styles of periodic table, which—akin to the “life-renewing goal” of the fictional quest—continue. (shrink)

Diagonal relationships in the periodic table were recognized by both Mendeléev and Newlands. More appropriately called isodiagonal relationships, the same three examples of lithium with magnesium, beryllium with aluminum, and boron with silicon, are commonly cited. Here, these three pairs of elements are discussed in detail, together with evidence of isodiagonal linkages elsewhere in the periodic table. General criteria for defining isodiagonality are proposed.

In a lengthy article E. Scerri and J. Worrall put forward the case for a novel ‘accommodationist’ version of the events surrounding the development of Mendeleef's Periodic Table 1869–1899. However these authors lay undue stress on the fact that President of the Royal Society of London Spottiswoode made absolutely no mention of Mendeleef's famous predictions in the Davy Medal eulogy in 1883 and undue stress on the fact that Cleve's classic 1879 Scandium paper contained an acknowledgement of Mendeleef's (...) prior prediction of eka-boron.They also fail to analyse in any detail the so-called ‘rare earth problem’ which, in the opinion of this author, causes problems for their account but not for a predictivist account. (shrink)

Within contemporary personality psychology there is widespread consensus that, at long last, the basic elements of "the" human personality have been empirically discovered, and that the systematic search for the underlying causes and consequences of personality differences can be pursued on this basis. The putatively basic trait dimensions are neuroticism, extraversion, openness, agreeableness, and conscientiousness, and are referred to collectively as "the Big Five." In the present article, this perspective on the psychology of personality is examined critically and found wanting. (...) It is argued that neither the "Big Five" framework in particular nor trait "psychology" more generally is adequate as the basis for a scientific psychology of the human person. 2012 APA, all rights reserved). (shrink)

The aim of this paper is to indicate the systematic place of arguments based on the concept of analogy within the theoretical framework of the Periodic Table of Arguments, a new method for describing and classifying arguments that integrates traditional dialectical accounts of arguments and fallacies and rhetorical accounts of the means of persuasion (logos, ethos, pathos) into a comprehensive framework. The paper begins with an inventory of existing approaches to arguments based on analogy, similarity and adjacent concepts. (...) Then, the theoretical framework of the table will be expounded and several concrete examples of arguments based on these concepts will be analyzed in terms of the framework. Finally, the results of these analyses will be summarized and it will be indicated how they can be refined in further research related to the Periodic Table of Arguments. (shrink)

The periodic table represents and organizes all known chemical elements on the basis of their properties. While the importance of this table in chemistry is uncontroversial, the role that it plays in scientific reasoning remains heavily disputed. Many philosophers deny the explanatory role of the table and insist that it is “merely” classificatory (Shapere, in F. Suppe (Ed.) The structure of scientific theories, University of Illinois Press, Illinois, 1977; Scerri in Erkenntnis 47:229–243, 1997). In particular, it (...) has been claimed that the table does not figure in causal explanation because it “does not reveal causal structure” (Woody in Science after the practice turn in the philosophy, history, and social studies of science, Routledge Taylor & Francis Group, New York, 2014). This paper provides an analysis of what it means to say that a scientific figure reveals causal structure and it argues that the modern periodic table does just this. It also clarifies why these “merely” classificatory claims have seemed so compelling–this is because these claims often focus on the earliest periodic tables, which lack the causal structure present in modern versions. (shrink)

This paper describes the construction of the Periodic Tables for cations of all elements with charges + 1, + 2, + 3 and anions with charge − 1. The Table for cations+1 differs significantly from other newly constructed Tables and from known Tables, as the d- and f-blocks are inserted into s-block and split it up for two parts. Importantly, a new type of 3d- and 4f-shell contractions has been discovered. The manifestations of secondary periodicity in case of (...) anions is absent or opposite to the manifestations observed for atoms and cations. For kainosymmetric anions, the ionization energies are lowered, which contradicts the theoretical assumptions and experimental data supporting the classical concept of kainosymmetry. Simple formulas are proposed for quantitative description of the manifestations of internal periodicity and kainosymmetry. The regularities of change in these manifestations depending on the charge and the position of ions or atoms in the Periodic Table are established. In the 6th period, the bifurcation in the properties characteristic of the internal periodicity does not occur at usual position, i.e. in the middle of the row from the block of the Periodic Table, but takes place earlier, along with the transition of the electronic configurations p2–p3. In other words, the place of transition from "early" to "late" elements changes. (shrink)

The thesis is: the “periodic table” of “dark matter” is equivalent to the standard periodic table of the visible matter being entangled. Thus, it is to consist of all possible entangled states of the atoms of chemical elements as quantum systems. In other words, an atom of any chemical element and as a quantum system, i.e. as a wave function, should be represented as a non-orthogonal in general (i.e. entangled) subspace of the separable complex Hilbert space (...) relevant to the system to which the atom at issue is related as a true part of it. The paper follows previous publications of mine stating that “dark matter” and “dark energy” are projections of arbitrarily entangled states on the cognitive “screen” of Einstein’s “Mach’s principle” in general relativity postulating that gravitational field can be generated only by mass or energy. (shrink)

Although the periodic system of elements is central to the study of chemistry and has been influential in the development of quantum theory and quantum mechanics, its study has been largely neglected in philosophy of science. The present article is a detailed criticism of one notable exception, an attempt by Hettema and Kuipers to axiomatize the periodic table and to discuss the reduction of chemistry in this context.

The debate about the relative epistemic weights carried in favour of a theory by predictions of new phenomena as opposed to accommodations of already known phenomena has a long history. We readdress the issue through a detailed re-examination of a particular historical case that has often been discussed in connection with it—that of Mendeleev and the prediction by his periodic law of the three ‘new’ elements, gallium, scandium and germanium. We find little support for the standard story that these (...) predictive successes were outstandingly important in the success of Mendeleev's scheme. Accommodations played an equal role—notably that of argon, the first of the ‘noble gases’ to be discovered; and the methodological situation in this chemical example turns out to be in interesting ways different from that in other cases—invariably from physics—that have been discussed in this connection. The historical episode when accurately analysed provides support for a different account of the relative weight of prediction and accommodation—one that is further articulated here. (shrink)

Some recent work in mathematical chemistry is discussed. It is claimed that quantum mechanics does not provide a conclusive means of classifying certain elements like hydrogen and helium into their appropriate groups. An alternative approach using atomic number triads is proposed and the validity of this approach is defended in the light of some predictions made via an information theoretic approach that suggests a connection between nuclear structure and electronic structure of atoms.

Demarcation of elements for two subsets appears to be the most fundamental approach to their classification. If one draws a vertical straight line through the middle of each block of elements in the Periodic table, all the elements are divided into two subsets: “early” and “later”. For example, in the d-block, the early ones are Sc–Mn, and the late ones, respectively, are Fe–Zn. Later elements partially repeat the properties of the early ones, and this is defined as the (...) internal periodicity. Another criterion for dividing the elements into two subsets is the evenness and oddness of the sum of n + l, where n is the principal quantum number, and l is the orbital quantum number for the outer electron subshells. Properties of the odd elements are closer to each other than to properties of even elements, and vice versa. This regularity is manifested as the secondary periodicity. The history of concepts, which considered the existence of subsets as well as of inner and secondary periodicities, is discussed. The features of the electronic structure, which underlie the existence of subsets, are considered. The existence of subsets was depicted earlier by dividing the periodic table into two tables or by applying a mirror-symmetric table. Small changes are proposed in the conventional Periodic table, allowing to reflect the existence of the considered subsets. (shrink)

Demarcation of elements for two subsets appears to be the most fundamental approach to their classification. If one draws a vertical straight line through the middle of each block of elements in the Periodic table, all the elements are divided into two subsets: “early” and “later”. For example, in the d-block, the early ones are Sc–Mn, and the late ones, respectively, are Fe–Zn. Later elements partially repeat the properties of the early ones, and this is defined as the (...) internal periodicity. Another criterion for dividing the elements into two subsets is the evenness and oddness of the sum of n + l, where n is the principal quantum number, and l is the orbital quantum number for the outer electron subshells. Properties of the odd elements are closer to each other than to properties of even elements, and vice versa. This regularity is manifested as the secondary periodicity. The history of concepts, which considered the existence of subsets as well as of inner and secondary periodicities, is discussed. The features of the electronic structure, which underlie the existence of subsets, are considered. The existence of subsets was depicted earlier by dividing the periodic table into two tables or by applying a mirror-symmetric table. Small changes are proposed in the conventional Periodic table, allowing to reflect the existence of the considered subsets. (shrink)

This is a comment on the paper by Barnes and the responses from Scerri and Worrall, debating the thesis that a fact successfully predicted by a theory is stronger evidence than a similar fact known before the prediction was made. Since Barnes and Scerri both use evidence presented in my paper on Mendeleev’s periodic law to support their views, I reiterate my own position on predictivism. I do not argue for or against predictivism in the normative sense that philosophers (...) of science employ, rather I describe how scientists themselves use facts and predictions to support their theories. I find wide variations, and no support for the assumption that scientists use a single ‘Scientific Method’ in deciding whether to accept a proposed new theory.Keywords: Predictivism; Novel predictions; Accommodation; Periodic law; Periodic table; Dmitri Mendeleev. (shrink)

We briefly describe in this paper the passage from Mendeleev’s chemistry (1869) to atomic physics (in the 1900’s), nuclear physics (in 1932) and particle physics (from 1953 to 2006). We show how the consideration of symmetries, largely used in physics since the end of the 1920’s, gave rise to a new format of the periodic table in the 1970’s. More specifically, this paper is concerned with the application of the group SO(4,2)⊗SU(2) to the periodic table of (...) chemical elements. It is shown how the Madelung rule of the atomic shell model can be used to set up a periodic table that can be further rationalized via the group SO(4,2)⊗SU(2) and some of its sub-groups. Qualitative results are obtained from this nonstandard table. (shrink)

There has been plenty of empirical evidence which shows that the single-particle picture holds to a good approximation in atomic nuclei. In this picture, protons and neutrons move independently inside a mean-field potential generated by an interaction among the nucleons. This leads to the concept of nuclear shells, similar to the electronic shells in atoms. In particular, the magic numbers due to closures of the nucleonic shells, corresponding to noble gases in elements, have been known to play an important role (...) in nuclear physics. Here we propose a periodic table for atomic nuclei, in which the elements are arranged according to the known nucleonic shells. The nuclear periodic table clearly indicates that nuclei in the vicinity of the magic numbers can be understood in terms of a shell closure with one or two additional nucleons or nucleon holes, while nuclei far from the magic numbers are characterized by nuclear deformation. (shrink)

No one knows yet how to organize, in a simple yet predictive form, the knowledge concerning the anatomical, biophysical, and molecular properties of neurons that are accumulating in thousands of publications every year. The situation is not dissimilar to the state of Chemistry prior to Mendeleev's tabulation of the elements. We propose that the patterns of presence or absence of axons and dendrites within known anatomical parcels may serve as the key principle to define neuron types. Just as the positions (...) of the elements in the periodic table indicate their potential to combine into molecules, axonal and dendritic distributions provide the blueprint for network connectivity. Furthermore, among the features commonly employed to describe neurons, morphology is considerably robust to experimental conditions. At the same time, this core classification scheme is suitable for aggregating biochemical, physiological, and synaptic information. (shrink)

The debate about the relative epistemic weights carried in favour of a theory by predictions of new phenomena as opposed to accommodations of already known phenomena has a long history. We readdress the issue through a detailed re-examination of a particular historical case that has often been discussed in connection with it-that of Mendeleev and the prediction by his periodic law of the three 'new' elements, gallium, scandium and germanium. We find little support for the standard story that these (...) predictive successes were outstandingly important in the success of Mendeleev's scheme. Accommodations played an equal role-notably that of argon, the first of the 'noble gases' to be discovered; and the methodological situation in this chemical example turns out to be in interesting ways different from that in other cases-invariably from physics-that have been discussed in this connection. The historical episode when accurately analysed provides support for a different account of the relative weight of prediction and accommodation-one that is further articulated here. (shrink)

The history of the diffusion and confirmation of Mendeleev’s periodic table of elements has proven to be a challenging testbed for contemporary philosophical debates on the role of predictions in science. More than ten years of fruitful literature came after Scerri and Worrall :407–452, 2001) versus Maher and Lipton ; nevertheless, such a long-lasting debate left quite a few open questions. The aim of this contribution is to go through the various cases that emerged during the debate, in (...) an effort to explain them coherently in a weak predictivist perspective. Maher’s early account—according to which the astounding success of the major predictions alone was enough to explain the confirmation of the periodic table—can now be replaced by a more balanced and thorough picture, where both predictions and accommodations do weight. (shrink)

A quick question! Who’s the first name that comes to mind when the periodic table is mentioned? Dmitrii Ivanovich Mendeleev is the obvious and universal answer. And the second name? Most of you would probably agree with my answer: Eric R. Scerri, Lecturer in Chemistry and History and Philosophy of Science at the University of California, Los Angeles, and founding editor of this journal, devoted to the philosophy of chemistry, another of his specialties.Through the years I have followed (...) Scerri’s work on the periodic table, reading his numerous articles and reviewing his two previous books (Scerri 2007; Laing and Kauffman 2007; Scerri 2009; Kauffman 2011). In his latest book he comprehensively but succinctly examines this true cultural iconic symbol of science that is used by artists, advertisers, and of course, scientists in all fields. It is almost as familiar to the general public as the chemical formula for water, and an understanding and appreciation for it is essential to the physi. (shrink)

Electronegativity, described by Linus Pauling described as “The power of an atom in a molecule to attract electrons to itself” (Pauling in The nature of the chemical bond, 3rd edn, Cornell University Press, Ithaca, p 88, 1960), is used to predict bond polarity. There are dozens of methods for empirically quantifying electronegativity including: the original thermochemical technique (Pauling in J Am Chem Soc 54:3570–3582, 1932), numerical averaging of the ionisation potential and electron affinity (Mulliken in J Chem Phys 2:782–784, 1934), (...) effective nuclear charge and covalent radius analysis (Sanderson in J Chem Phys 23:2467, 1955) and the averaged successive ionisation energies of an element’s valence electrons (Martynov and Batsanov in Zhurnal Neorganicheskoi Khimii 5:3171–3175, 1980), etc. Indeed, there are such strong correlations between numerous atomic parameters—physical and chemical—that the term “electronegativity” integrates them into a single dimensionless number between 0.78 and 4.00 that can be used to predict/describe/model much of an element’s physical character and chemical behaviour. The design of the common and popular medium form of the periodic table is in large part determined by four quantum numbers and four associated rules. However, adding electronegativity completes the construction so that it displays the multi-parameter periodic law operating in two dimensions, down the groups and across the periods, with minimal ambiguity. (shrink)

This article carefully analyzes a recent paper by Weisberg in which it is claimed that when Mendeleev discovered the periodic table he was not working as a modeler but instead as a theorist. I argue that Weisberg is mistaken in several respects and that the periodic table should be regarded as a classification, not as a theory. In the second part of the article an attempt is made to elevate the status of classifications by suggesting that (...) they provide a form of ‘side-ways explanation’. (shrink)

The purpose of this paper is to propose a new design for the presentation of the periodic system of the elements. It is a system that highlights the fundamental importance of elements as basic substances rather than elements as simple substances. Furthermore the fundamental nature of atomic number triads of elements is put to use in obtaining a new perfect triad by relocating hydrogen among the halogens to give the triad H, F, Cl. An unexpected regularity in the period (...) lengths of successive rows is obtained on rearranging the table to start with the halogens on the left-hand side. The relative virtues of this table, as compared with the medium-long form and the left-step table, are discussed. (shrink)

This chapter gives an overview of the evolution of the position of the rare-earth elements in the periodic system, from Mendeleev’s time to the present. Three fundamentally different accommodation methodologies have been proposed over the years. Mendeleev considered the rare-earth elements as homologues of the other elements. Other chemists looked upon the rare earths as forming a special intraperiodic group and therefore clustered the rare-earth elements in one of the groups of the periodic table. Still others adhered (...) to the intergroup accommodation of the rare earths, according to which the rare-earth elements do not show any relationship with the other elements, so that they had to be placed within the periodic table as a separate family of elements. The intergroup accommodation became the preferred one in the twentieth century. The advantages and disadvantages of the different representations of the modern periodic table are discussed. (shrink)

A critique is given of the attempt by Hettema and Kuipers to formalize the periodic table. In particular I dispute their notions of identifying a naïve periodic table with tables having a constant periodicity of eight elements and their views on the different conceptions of the atom by chemists and physicists. The views of Hettema and Kuipers on the reduction of the periodic system to atomic physics are also considered critically.

The lanthanide elements from lanthanum to lutetium inclusive are incorporated into the body of the periodic table. They are subdivided into three sub-groups according to their important oxidation states: La to Sm, Eu to Tm, Yb and Lu, so that Eu and Yb fall directly below Ba; La, Gd, Lu form a column directly below Y; Ce and Tb fall in a vertical line between Zr and Hf. Pm falls below Tc; both are radioactive, and not naturally occurring. (...) The elements with easily attained 2+ and 4+ oxidation states are grouped and clearly differentiated. Gadolinium has an important position as the centre of four triads in the block of elements that surround it– La, Gd, Lu; Ba, Gd, Hf; Eu, Gd, Tb; Yb, Gd, Ce. This new arrangement has the advantages of compactness, simplicity and clarity – there are no tie lines; and important oxidation states of these metals are emphasized. The actinides are also accommodated within this system, and element 114 falls naturally below lead in Group 14. (shrink)

In a paper from 2001, Michael C. Rea considers the question of what pornography is. First, he examines a number of existing definitions of ‘pornography’ and after having rejected them all, he goes on to present his own preferred definition. In this short paper, I suggest a counterexample to Rea’s definition. In particular, I suggest that there is something that, on the one hand, is pornography according to Rea’s definition, but, on the other hand, is not something that we would (...) intuitively describe as being an instance of pornography. (shrink)

The article examines a recent interventionist account of causation by Ross, in which electronic configurations of atoms are considered to be the cause of chemical behavior. More specifically I respond to the claim that a change in electronic configuration of an atom, such as occurs in the artificial synthesis of elements, causes a change in the behavior of the atom in question. I argue that chemical behavior is governed as much by the nuclear charge of an atom as it is (...) by its electronic structure. It is suggested that an adequate analysis requires attention to the dynamical interactions between nuclear charges and those of electrons, as typically carried out through the application of the Schrödinger equation. It is concluded that electronic configurations can only be said be causal in a weak sense that is somewhat analogous to the causal arguments that are invoked in folk physics. (shrink)

Predictivism is the view that successful predictions of “novel” evidence carry more confirmational weight than accommodations of already known evidence. Novelty, in this context, has traditionally been conceived of as temporal novelty. However temporal predictivism has been criticized for lacking a rationale: why should the time order of theory and evidence matter? Instead, it has been proposed, novelty should be construed in terms of use-novelty, according to which evidence is novel if it was not used in the construction of a (...) theory. Only if evidence is use-novel can it fully support the theory entailing it. As I point out in this paper, the writings of the most influential proponent of use-novelty contain a weaker and a stronger version of use-novelty. However both versions, I argue, are problematic. With regard to the appraisal of Mendeleev’ periodic table, the most contentious historical case in the predictivism debate, I argue that temporal predictivism is indeed supported, although in ways not previously appreciated. On the basis of this case, I argue for a form of so-called symptomatic predictivism according to which temporally novel predictions carry more confirmational weight only insofar as they reveal the theory’s presumed coherence of facts as real. (shrink)

At the heart of chemistry lies the periodic system of chemical elements. Despite being the cornerstone of modern chemistry, the overall structure of the periodic system has never been fully understood from an atomic physics point of view. Group-theoretical models have been proposed instead, but they suffer from several limitations. Among others, the identification of the correct symmetry group and its decomposition into subgroups has remained a problem to this day. In an effort to deepen our limited understanding (...) of the periodic law, we have extended the traditional Lie algebraic framework to account for the peculiar degeneracy structure of the periodic system. Starting from the four-dimensional hidden symmetry and accidental degeneracy of the hydrogen atom, as first revealed by Fock in 1935, our research has mainly focussed on the way this SO(4) symmetry of the Coulomb potential gets broken in the periodic system as a consequence of the transformation of the hydrogenic (n, l) filling order to the Madelung (n+l, n) order due to electronic repulsions, relativistic effects and spin-orbit couplings. In this PhD dissertation, a new left-step format of the periodic table is first proposed on the basis of the Madelung rule. Following the particle physics tradition, the chemical elements are then considered as various states of some 'atomic matter', which is described by a non-compact spectrum-generating dynamical Lie group. The chemical elements are shown to form a basis for a single infinite-dimensional degeneracy space of the SO(4,2) ⊗ SU(2) group. An explanation for the period doubling is then proposed in terms of a particular symmetry breaking of the SO(4,2) group to the anti de Sitter SO(3,2) group. The Madelung rule is rationalised on the basis of nonlinear Lie algebras which reflect the screening of the Coulomb hole. This opens new perspectives for a symmetry-based understanding of how the periodic law emerges from its quantum mechanical foundations, and holds the future promise of complementing our current phenomenological approach by a direct atomic physics approach. (shrink)

The basis of the Periodic Table is discussed. Electronic configuration recurs in only 21 out of the 32 groups. A better basis is derived by considering the highest classical valency (v) exhibited by an element and a new measure, the highest valency in carbonyl compounds (v*). This leads to a table based on the number of outer electrons possessed by an atom (N) and the number of electrons required for it to achieve an inert (noble) gas configuration (...) (N*). Periodicity of these is nearly complete. The new basis helps to settle the question of the best form of table and related issues. (shrink)

Many different arguments have been put forward in order to assign the best place for a given element within Mendeleev's Table: its spectroscopy, its chemical activity, the crystalline structure of its solid state, etc. We here propose another criterion; the nature of the few body corrections to the pairwise additive energy. This argument is used here to address a question often brought forward by Eric Scerri in Foundations of Chemistry, namely the rightful place of helium; either above the column (...) of the alkaline earths (beryllium, etc.) or rather above the noble gas elements. (shrink)

Group 3 as Sc–Y–La, rather than Sc–Y–Lu, dominates the literature. The history of this situation, including involvement by the IUPAC, is summarised. I step back from the minutiae of physical, chemical, and electronic properties and explore considerations of regularity and symmetry, natural kinds, and quantum mechanics, finding these to be inconclusive. Continuing the theme, a series of ten interlocking arguments, in the context of a chemistry-based periodic table, are presented in support of lanthanum in Group 3. In so (...) doing, I seek to demonstrate a new way of thinking about this matter. The last of my ten arguments is recast as a twenty-word categorical philosophical (viewpoint-based) statement. (shrink)