Elements and Atoms: Case Studies in the Development of Chemistry

View translations into Romanian by Alexander Ovsov and Ukrainian by Vlad Brown.

Preface and Contents

My intention here is to collect several articles by scientists who contributed to the development of knowledge about atoms and elements, and to provide sufficient background and commentary to place the work of these pioneers in context. In addition, I attempt to teach about how science is done by examining the work of particular scientists in their own words and adding to their articles annotations designed to emphasize the researchers' methodology. This work, then, overlaps in purpose several kinds of works in chemistry or the history of chemistry; however, it has different emphases as well. The present work is not intended to be a history of chemistry. I do not claim for it the breadth or comprehensiveness of a history, but rather a selective attention in detail to several important works in the areas of atoms and elements. Nor is this work intended to be an anthology of classic papers in chemistry. Again, it has less breadth but more detail--in particular detail that I hope makes the book's selections comprehensible to interested non-scientists as well as to students and teachers of chemistry and professional chemists.

Taken as a group, the articles illustrate development of the concepts of element and atom. The first set examine the idea of element from the pre-scientific four elements of the ancients to the empirical and provisional notion of elements as the ultimate products of chemical analysis. The next set concern the atom and the atomic-molecular theory proposed by Dalton and modified by Gay-Lussac and Avogadro. Next, attention returns to elements, and in particular to their classification: the law of octaves of Newlands, the periodic system of Mendeleev, and the admission into that system of the previously unsuspected noble gases. Finally (for the book at any rate), the last set of cases treat the realization that the atom has pieces and is not indivisible.

Of course, scientific understanding of atom and element did not stop evolving in 1913, the publication date of the last annotated paper in this collection. Quantum theory is crucial to a modern view of the structure of atoms and molecules, and a still deeper understanding of the nucleus is needed to explain what distinguishes one element from another and one isotope from another. But those are other stories.

The closest antecedents to the present work are the case histories in science described and advocated by James Bryant Conant [Conant 1957]. I embrace Conant's notion that the work of great scientists of the past can be used to illustrate the practice of science to educated people who are not familiar with the working of science. I maintain further that cases from the history of chemistry merit detailed study from students and teachers of chemistry as well, presenting an opportunity to learn some of the history of their field as well as how some of its great practitioners operated.

My approach differs from Conant's in format and organization. Each of the following chapters is built around words of an original researcher. A selection from the researcher's writings, whether the formal announcement of a discovery to the scientific community at the time or a later retrospective on previous work, stands in the foreground of each case. Each selection is also preceded by a brief introduction and followed by a list of references. Extensive commentary on each selection is presented in the form of footnotes. These notes explain terms, provide additional historical details, or draw attention to methodological or pedagogical points. The purpose of the notes is to facilitate the close reading of the original articles by different groups of readers with a variety of interests and background knowledge. I have also taken advantage of some of the opportunities the Internet offers. In addition to hyperlinks from chapter to chapter within this work, there are links to other papers posted at my Classic Chemistry website and John Park's ChemTeam site, links to glossary definitions at Classic Chemistry, and illustrations of protagonists from a variety of Internet sites.


James Bryant Conant, Ed., Harvard Case Histories in Experimental Science, 2 vols (Cambridge, MA: Harvard,1957).



  1. Four elements: Aristotle, De Generatione et Corruptione
  2. Elements from experiment, not philosophy: Boyle, The Sceptical Chymist
  3. Elements are undecomposed bodies: Lavoisier, Elements of Chemistry preface
  4. Air is not an element: Priestley, Experiments and Observations on Different Kinds of Air
  5. Fire and earth are not elements: Lavoisier, Mémoires de l'Académie Royale des Sciences, p. 520 (1775)
  6. Water is not an element: Lavoisier, Observations sur la physique (1783)


  7. Identical particles with characteristic weights: Dalton, New System of Chemical Philosophy
  8. Combination of gases in simple ratios by volume: Gay-Lussac, Mémoires de la Société d'Arcueil 2, 207 (1808)
  9. Avogadro's hypothesis: Avogadro, Journal de physique 73, 58 (1811)
  10. Prout's hypothesis: Prout, Annals of Philosophy 6, 321 (1815); 7, 111 (1816)

    Classification of Elements: Periodic System

  11. An unsystematic foreshadowing: Newlands, Chemical News (1863-66)
  12. Mendeleev's early table: Mendeleev Zeitschrift für Chemie 12, 405 (1869)
  13. Mendeleev's later reflections: Mendeleev, Journal of the Chemical Society 55, 634 (1889)
  14. Argon, a new element: Rayleigh, "Argon," Royal Institution Proceedings 14, 524 (1895)
  15. A place for the noble gases: Ramsay, "An Undiscovered Gas," Nature 56, 378 (1897)

    Back to the Atom: Indivisible no Longer

  16. Electron: Thomson, Nobel Prize in Physics Award Address, 1906
  17. Discovery of Radioactivity: Becquerel, Comptes Rendus 122, 420 (1896); 501 (1896)
  18. Radioactivity as an atomic phenomenon: Curie, Comptes Rendus 126, 1101-3 (1898)
  19. Nature of α-particles: Rutherford and Royds, Philosophical Magazine 17, 281-6 (1909)
  20. Isotopes: Soddy, "Radioactivity," Chemical Society Annual Reports 10, 262-88 (1913)

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