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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.

Use the drop menus below to search & select from the more than 1100 Period Tables in the database:

  Text Search:       

The 10 Periodic Tables most recently added to the database:

2023   Semicircular Hybrid Chart of the Nuclides
2023   Six Stages of The Convergence of The Periodic System
2023   Kudan's Periodic System
1900   History of the Discovery of the Group 18 (erstwhile Group 0) Elements
2023   Element Names: The Etymology of The Periodic Table
2007   Seeger-Quadbeck Periodic Table
2022   BacklightPower Periodic Table of the First 21 Elements
2023   Marks' Version of Mendeleyev's 1869 Formulation
2023   Mendeleyev’s Periodic Table after Ramsay & Sommerfeld
2018   Short Form of Mendeleev’s Periodic Table of Chemical Elements


Semicircular Hybrid Chart of the Nuclides

Nawa Nagayasu has produced a new version of the Segrè Chart of the Nuclides.

Nawa writes:

"The chart has the number of neutrons on the [curved] horizontal axis and the number of protons (atomic number) on the vertical axis. I used the IAEA colour coding [scheme]. JAEA's half-life ranks are indicated by simple numbers, not rounded frames.

"In order to fit the whole chart into a semicircle, the axis representing the number of neutrons was made a spiral-like curve. For clarity, the number of neutrons is shown in the middle of each curve."

Yuri Oganessian has commented:

"Nawa Nagayasu is an original and talented designer. After all, it is not easy to work with 118 elements, but now also with isotopes, of which there are more than 3000. The fan design looks attractive and this is very important. This will make people, especially school age, guess the numbers that are written there. So they will gradually delve into the content of the Table, a truly brilliant creation."

Click image to enlarge

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Six Stages of The Convergence of The Periodic System

Bran, A.M., Stadler, P.F., Jost, J. et al. The six stages of the convergence of the periodic system to its final structureCommun Chem 6, 87 (2023).

Abstract (abridged):

"We show, by analysing the space between 1800 and 2021, that the system has converged towards its current stable structure through six stages, respectively characterised by the finding of elements (1800–1826), the emergence of the core structure of the system (1826–1860), its organic chemistry bias (1860–1900) and its further stabilisation (1900–1948), World War 2 new chemistry (1948–1980) and the system final stabilisation (1980–)."

Periodic tables representative of each period in history. Families of similar elements (sets sharing colour) shown in each table summarise the patterns and do not necessarily imply continuity nor simultaneity of the families throughout the period:

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Kudan's Periodic System

From Pavel V. Kudan, a specialist in mass-spectrometry and identification of compounds, who suggests new periodic table based on new formulation of the periodic law.

See also:

Kudan's Periodic Law (Helix Form)

Genoma de la Materia

Click the image to enlarge.

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History of the Discovery of the Group 18 (erstwhile Group 0) Elements

John Marks has provided a concise history of the discovery of the Group 18 elements and the element name"Nitron/Radon".

Radioactivity was discovered by Becquerel in 1896 and the Curies noted transferred radioactivity rather like the induction of electric or magnetic charge. Radon was discovered in 1900, by Dorn in Halle; Rutherford discovered thoron in 1899; and Debierne discovered actinon in 1903. The time-line is:

So niton (from Latin nitens = shining) was noticed by the Curies in 1899 as an emanation from radium. That same year Rutherford noted an identical emanation from thorium, and in 1903 Debierne discovered the same emanation from actinium. All three ('radon', 'thoron' and 'actinon') were identified as an element by Ramsay in 1904 and characterized by him in 1909.

Ramsay named the element niton after its most prominent property viz. that it glowed in the dark.

With the introduction of Soddy's isotopes, it became clear that: thoron was Nt-220, radon was Nt-222 & actinon was Nt-219.

There are natural traces of other isotopes (e.g. Nt-217, Nt-218) from beta disintegration of astatine. So "radon" was just one isotope of niton.

The foregoing history of niton is uncontroversial and the name niton, Nt, for Z = 86 dates at least from Professor Young´s textbook of stoichiometry in 1908.

In 1912, the name 'niton' was adopted by the International Commission for Atomic weights. Rydberg's PT of 1913 has Nt as the last inert gas, as does Irving Langmuir's PT of 1919, Niels Bohr's PT of 1922, GN Lewis's PT of 1923 and even the CRC's Handbook of Chemistry and Physics in 1924.

John Marks concludes:

"Niton, Nt, for Z = 86, was thus established by its discoverers and accepted by the chemistry (and physics) establishment. Radon, Rn, is an error perpetuated by IUPAC [amongst its many sins].

"Radon is an isotope. We do not refer to hydrogen as 'protium', so why are we referring to niton as 'radon'?"

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Element Names: The Etymology of The Periodic Table

An excellent video by RobWords about the names of the chemical elements and how they came about:

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Seeger-Quadbeck Periodic Table

Seeger-Quadbeck H-J 2007, World of the Elements Elements of the World, Wiley-VCH, Wienheim, inside cover.

René Vernon, who provided the graphic, writes:

"An example of a rarely seen 32-column table. The categorisation scheme is interesting.

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BacklightPower Periodic Table of the First 21 Elements

Periodic Table of The First Twenty-Electron-Atoms Solved With the Grand Unified Theory of Classical Physics by Backlight Power.

Click the image or here to go to the origional PDF:

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Marks' Version of Mendeleyev's 1869 Formulation

John Marks, who provided the graphic, writes:

"I went back to Mendeleyev´s 1869 original and drew this (below) which demonstrates the Sommerfeldsche aufspaltung as occurring after completed s-subshells. No-one disputes the chemical phenomena of the octets formed by He/Ne, Li/Na, Be/Mg, B/Al, C/Si, N/P and O/S nor that H/F occurs at the beginning of these octets, however "irregular" H may appear.

"Chemical periodicity is clearly based on periods arising from sp3 hybridization and the aufspaltung appears to occur between the s and the p3. This gives rise to the positions of Sommerfeld's "Long" (with the d-elements) and "Very Long" (with the f-elements) periods."

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Mendeleyev’s Periodic Table after Ramsay & Sommerfeld

John Marks, who provided the graphic, writes:

"This is the Ramsay-Sommerfeld PT and would seem to be the definitive PT, at least historically.

"Ramsay, a chemist, completed Mendeleyev's PT with the discovery of the inert gases in the 1890s and the position of hydrogen with the halogens by 1915.

"Sommerfeld, a physicist, generalized Bohr's atom in 1916 to yield the s-, p-, d- and f- electronic subshells that determine the layout of physicists' PTs, in particular their first "very short" period comprising H and He. Sommerfeld also explained the 'long periods', viz. the transition series ('A' subgroups) and the 'very long periods', viz. the rare earth series ('B' subgroups).

"In this chemistry/physics hybrid periodic table, the physicist Sommerfeld's first ('very short') "period" is subsumed under the chemist Ramsay's first two groups (-1 and 0) which are distinguished by colour: group -1 is white = 1s1p5, viz. H & the halogens; group 0 is black = 1s2p6, viz. He & the inert gases.

"Einstein's demonstration of atomic reality in 1905 (phenomena verified by Perrin in 1908) established the basic units of the paradigm of chemistry. Rutherford and Bohr (both physicists) went inside the atom, into the paradigm of physics.

"The PT thus straddles the borderland of the two paradigms of physics and chemistry and this has contributed significantly to the long debates on the form of the PT."

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Short Form of Mendeleev’s Periodic Table of Chemical Elements

Andriiko, A.A., Lunk, HJ. The short form of Mendeleev’s Periodic Table of Chemical  Elements: toolbox for learning the basics of inorganic chemistry. A contribution to celebrate 150 years of the Periodic Table in 2019. ChemTexts 4, 4 (2018).

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What is the Periodic Table Showing? Periodicity

© Mark R. Leach Ph.D. 1999 –

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