Periodic Table |
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| What is the Periodic Table Showing? | Periodicity |
The INTERNET Database of Periodic Tables
There are thousands of periodic tables in web space, but this is the only comprehensive database of periodic tables & periodic system formulations. If you know of an interesting periodic table that is missing, please contact the database curator: Mark R. Leach Ph.D. The database holds information on periodic tables, the discovery of the elements, the elucidation of atomic weights and the discovery of atomic structure (and much, much more).
The 10 most recent entries to the database:
| Year: 2026 | PT id = 1393, Type = element review |
What is an element, and how is it defined in the IUPAC Gold Book?
A recent publication by Eric Scerri: What is an element, and how is it defined in the IUPAC Gold Book?
Read the paper or download the PDF here, or go to page 36 of the Chemistry International journal here.
| Year: 1930 | PT id = 1392, Type = formulation |
Periodisches System der Elemente
Posted on Wikimedia by LukaszKatlewa who writes:
"Periodisches System der Elemente (1904-1945, now at the Gdansk University of Technology): lack of elements: 84 polonium Po (though discovered as early as in 1898 by Maria Sklodowska-Curie), 85 astatine At (1940, in Berkeley), 87 francium Fr (1939, in France), 93 neptunium Np (1940, in Berkeley) and other actinides and lanthanides. Old symbols for: 18 argon Ar (here: A), 43 technetium Tc (Ma, masurium, 1925, dismissed as an error and finally confirmed in 1937, Palermo), 54 xenon Xe (X), 86 radon, Rn (Em, emanation)."
Mark Leach writes: "I would guess the date at 1930."

| Year: 2026 | PT id = 1391, Type = element review |
6 Times Scientists Were Wrong About the Periodic Table
A video from SciShow discussing six times scientists made incorrect predictions about chemical elements: Coronium; Nebulium (Nebulium, Nephium, Nephelium); Masurium (Davium, Leucium, Neponium... actually Technecium); Florencium/Illinium (actually Promethium); Ausenium; and Hesperium.
| Year: 1928 | PT id = 1390, Type = formulation spiral |
Another Attempt to Base a Classification of The Elements on Atomic Structure
Simpson, O.J., Another Attempt to Base a Classification of The Elements on Atomic Structure, J. Chem. Educ. 1928, 5, 1, 57 doi.org/10.1021/ed005p57:

| Year: 2023 | PT id = 1389, Type = review formulation |
La Tabla Periódica. El poder de la sistematización. La importancia de la precisión
A video of a presentation (in Spanish) by Manuel Yáñez, a professor at the Autonomous University entitled: La Tabla Periódica. El poder de la sistematización. La importancia de la precisión (The Periodic Table. The power of systematization. The importance of precision.)
| Year: 2020 | PT id = 1388, Type = formulation 3D spiral |
Alexander's Quad Block/neXus/IIIc Model
Roy Alexander's Quad Block/neXus/IIIc Model.


| Year: 1953 | PT id = 1387, Type = formulation 3D spiral |
Kapustinsky's Pyrimid
Kapustinsky, A. F. (1953). Periodicity in the structure of the electron envelopes and nuclei of atoms Communication 1. Periodic system of the elements and its connection with the theory of numbers and with physicochemical analysis. Bulletin of the Academy of Sciences of the USSR Division of Chemical Science, 2(1), 1–9. Paper as pdf.
Thanks to René Vernon for the tip!
| Year: 1919 | PT id = 1386, Type = formulation |
Hackh's Classification of The Chemical Elements
Hackh, I. W. D. (1919). The classification of the chemical elements: The fundament of chemistry, Scientific American, 87 (supp. no. 2253), pp. 146–149 (148). https://zenodo.org/records/2454321
René Vernon writes:
Note that Group 4 (including Lu) appears twice, on the left and right.
Hackh does not get it quite right when he refers to a vertical similarity prevailing in the upper half of the table and a horizontal similarity in the lower half. A horizontal similarity prevails along the first row of the transition metals; vertical similarities tend to prevail among the second and third row dyads of the transition metals. That said, a horizontal similarity does prevail among the lanthanides.
On the noble gases, Hackh (p. 146) wrote: "...they combined the two extreme ends of a period, they formed the bridge from a non-metallic halogen (electro-negative element) to a metallic alkali (electro-positive element). For this reason we may speak of these elements, the rare or inert gases, as the terminals of the periods, which are either positive nor negative... The first three elements following an inert gas are always strong positive, while the last three before an inert gas are always strong negative and thus a kind of a transition is formed by the fourth element, or the elements of the carbon group."
For chemical properties he wrote: "The chemical characteristics of the elements can equally well be studied, for there are the acid- and base-forming elements on the chart, whose zones gradually infiltrate from strong basic to weak basic to atmospheric to weak acid to strong acid or vice versa."
Read more in the paper.
| Year: 1905 | PT id = 1385, Type = structure |
Einstein's Annus Mirabilis
The annus mirabilis papers (from Latin: annus mirabilis, 'miraculous year') are four papers that Albert Einstein published in the scientific journal Annalen der Physik (Annals of Physics) in 1905. As major contributions to the foundation of modern physics, these scientific publications were the ones for which he gained fame among physicists. They revolutionised science's understanding of the fundamental concepts of space, time, mass, energy, atoms and atomic structure.
- Einstein, Albert (1905) Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt [On a Heuristic Point of View about the Creation and Conversion of Light] Annalen der Physik (in German). 17 (6): 132–148. doi: https://doi.org/10.1002%2Fandp.19053220607 English translation.
The first paper explained the photoelectric effect, which established the energy of the light quanta, E = hf or E = hν (depending upon context), where h = Planck's constant. This was the only specific discovery mentioned in the citation awarding Einstein the 1921 Nobel Prize in Physics.
- Einstein, Albert (1905) Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen [Investigations on the theory of Brownian Movement] Annalen der Physik (in German). 322 (8): 549–560. doi: https://doi.org/10.1002%2Fandp.19053220806
The second paper explained Brownian motion, D = μkBT which compelled physicists to accept the existence of atoms.
- Einstein, Albert (30 June 1905) Zur Elektrodynamik bewegter Körper [On the Electrodynamics of Moving Bodies]. Annalen der Physik (in German). 17 (10): 891–921. doi: https://onlinelibrary.wiley.com/doi/10.1002/andp.19053221004 English tranlation
The third paper introduced Einstein's special theory of relativity, which proclaims the constancy of the speed of light.
- Einstein, Albert (1905). Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig? [Does the Inertia of a Body Depend Upon Its Energy Content?] Annalen der Physik (in German). 18 (13): 639–641. doi: https://onlinelibrary.wiley.com/doi/10.1002/andp.19053231314 English translation
The fourth, a consequence of special relativity, developed the principle of mass–energy equivalence, expressed in the equation E = mc2, and which led to the discovery and use of nuclear power decades later.
These four papers, together with quantum mechanics and Einstein's later general theory of relativity (1916), are the foundation of modern physics.

| Year: 1926 | PT id = 1384, Type = structure |
Schrödinger and The Hydrogen Atom
In Parts II and III of Schrödinger's 1926 papers: Annalen der Physik, 79 (1926), pp. 361–376 and Annalen der Physik, 80 (1926), pp. 437–490, the hydrogen atom is addressed.
Here Schrödinger:
- Separates the equation in spherical coordinates
- Solves the radial equation
- Derives hydrogen energy levels:

- Shows agreement with the Bohr spectrum
This is the first full wave-mechanical derivation of hydrogen.
There is an on-line English translation of Schrödinger's 1926 papers, published in 1928.

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| What is the Periodic Table Showing? | Periodicity |
© Mark R. Leach Ph.D. 1999 –
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