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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   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
2022   Ramsay-Sommerfeld Periodic Table
2022   Periodic Table of Periodic Tables


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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Ramsay-Sommerfeld Periodic Table

John Marks has updated Scerri's 2006 Triad formulation. Marks writes:

"[This is] an expansion of Scerri´s 2006 triad formulation, but brings the lanthanides & actinides in from the cold. It is lso modelled on the way IUPAC constructed its 18-group PT (but with traditional group numbering), that is to say, the total of 22 groups is simply IUPAC's 18 plus the four extra f-groups. I am not sure if this counts as a "medium" or a "long" form.

"If this PT needs a name, it would be the Ramsay-Sommerfeld PT. It has Ramsay´s 1915 arrangement for H (copied by Eric Scerri in 2006) and Sommerfeld's "greater" and "lesser" periods (1916) in green and yellow respectively. It solves the 'exile' of the f-blocks without making it too unwieldy (22 instead of 32 groups). The yellow (transition series) are Sommerfeld's 'A' subgroups and the green (rare earth series) are Sommerfeld's 'B' subgroups."

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Periodic Table of Periodic Tables

René Vernon has collected the PT formulations in this PT database and classifed them as:

Short, Triangular, Medium, Long, Continious, Folding, Spatial & Unclassified

and tabulated them by date. The 'working document' is currently a word file.

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What is the Periodic Table Showing? Periodicity

© Mark R. Leach Ph.D. 1999 –

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