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  Web Book Home Page | Chemogenesis Main Index Foreword:  Chemogenesis & Chemical Education Part I   Atoms | Elements | Periodic Tables 1.1  Introduction to Chemogenesis 1.2  Nucleosynthesis of The Elements 1.3  The Segrè Chart 1.4  Quantum Numbers to Periodic Tables 1.5  The Periodic Table: What Is It Showing? 1.6  The INTERNET Database of Periodic Tables 1.7  Periodicity Part II   Structure | Bonding | Material Type 2.1  Mono-Bond Typed Binary Compounds 2.2  Binary Compound Synthlet 2.3  Electronegativity 2.4  van Arkel-Ketelaar Triangles of Bonding 2.5  Tetrahedra of Structure, Bonding & Material Type 2.6  Structure, Bonding & Material Synthlet 2.7  The Classification of Matter: Chemical Stuff Part III   Interactions | Reactions | Mechanisms 3.1  The Chemogenesis Analysis: An Overview 3.2  Lewis and Brønsted Models of Acidity 3.3  The Hard Soft [Lewis] Acid Base Principle 3.4  Main Group Elemental Hydrides 3.5  Five Hydrogen Probe Experiments 3.6  Congeneric Dots, Series & Planars 3.7  Quantifying Congeneric Behaviour 3.8  Ligand Replacement Congeneric Series 3.9  Congeneric Array Interactions 3.10  Emergence of Organic Chemistry 3.11  Congeneric Array Database 3.12  The Five Reaction Chemistries 3.13  Lewis Acids & Lewis Bases: A New Analysis 3.14  The Lewis Acid/Base Interaction Matrix 3.15  Patterns in Reaction Chemistry Poster 3.16  Lewis Acid/Base Interaction Matrix Database 3.17  Nucleophiles, Bases & The Fluoride Ion 3.18  Redox Chemistry 3.19  Redox Chemistry Synthlet 3.20  Radical Chemistry 3.21  Diradical Chemistry 3.22  Photochemistry 3.23  Species/Species Interactions 3.24  The Simplest Mechanistic Step: STAD 3.25  Unit & Compound Mechanistic Steps 3.26  The Mechanism Matrix 3.27  Addition To A Double Bond Synthlet 3.28  Pericyclic Reaction Chemistry Part IV   Chemical Theory 4.1  Why Do Chemical Reactions Occur? 4.2a  Thermochemistry: List Reactions Synthlet 4.2b  Thermochemistry: Play With Reaction Synthlet 4.2c  Thermochemistry: Bulid A Reaction Synthlet 4.3  Timeline of Structural Theory 4.4  Modern Lewis Theory 4.5  Valence Shell Electron Pair Repulsion: VSEPR 4.6  Diatomic Species by Molecular Orbital Theory 4.7  Polyatomic Species: Molecular Orbitals 4.8  Organic π-Systems 4.9  Functional Group Database Part V   Complexity & Emergence 5.1  Chemistry & Complexity: Systems 5.2  Linear Chemistry Systems 5.3  Chemical Systems Prone to Complexity Part VI   Extras 6.1  Chemogenesis Videos 6.2  Chemical Thesaurus Reaction Chemistry Database 6.3  Chemogenesis Paper 6.4  Electronegativity as a Basic Elemental Property 6.5  Literature References & Further Reading

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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 1300 Period Tables in the database: 

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Periodic Tables from the year 1950:

The Modern Periodic Table

The modern periodic table is based on quantum numbers and blocks, here.

A periodic table can be constructed by listing the elements by n and l quantum number:

The problem with this mapping is that the generated sequence is not continuous with respect to atomic number atomic number, Z: Check out the sequence Ar to K, 18 to 19.

Named after a French chemist who first published in the formulation in 1929, the Janet or Left-Step Periodic Table uses a slightly different mapping:

While the Janet periodic table is very logical and clear it does not separate metals from non-metals as well as the Mendeleev version, and helium is a problem chemically.

However, it is a simple mapping to go from the Janet or Left-Step periodic table to a modern formulation of Mendeleev's periodic table:

On this page web, "full" f-block included periodic tables are shown wherever possible, as above.

However, the periodic table is usually exhibited in book and on posters in a compressed form with the f-block "rare earths" separated away from the s-block, p-block and d-block elements:

However, the compression used introduces the well known problem known as a "fence post error".

The effect is that:

La and Ac: move from f-block to d-block
Lu and Lr: move from p-block to f-block

Chemically, the elements can be fitted in and classified either way. Many thanks to JD for pointing the situation with the periodic table is a fence post error.

Mark Winter's Web Elements project, here, uses the formulation shown below:

Interestingly, the IUPAC periodic table separates out 15 lanthanides, La-Lu, and 15 actinides, Ac-Lr by leaving gaps in period 3 under Sc & Y:

This corresponds to:

By Mark Leach

Clark's Updated Periodic Table

John D Clark's 1950 chart. It looks as though the experience of producing the 1949 version for Life Magazine caused him to have a radical rethink. John D. Clark, A modern periodic chart of chemical elements. Science,111, 661-663 (1950). Information supplied by Philip Stewart.

Scheele's System

Scheele's system of 1950 (from van Spronsen):

Elements Known in the Year 1950

Elements known in the year 1950, taken from this Wikipedia page:

Discovery of Californium

Californium, atomic number 98, has a mass of 251 au.

Synthetic radioactive element.

Californium was first observed in 1950 by S. G. Thompson, K. Street, Jr., A. Ghiorso and G. T. Seaborg.

• Wikipedia
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• Periodictable.com
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Sidgwick's Periodic Classification (Mendeleeff)

From N.V. Sidgwick, Chemical Elements and Their Compounds, vol. 1, Oxford University, London, p. xxviii (1950).

René Vernon writes:

"In this curious table the Lanthanides are located in group IIIA while the Actinides have been fragmented.

Instead:

• Ac, Th, and Pa are located in groups IIIA, IVA and VA under Lu, Hf, and Ta, respectively
• The uranides, U, Np, Pu, Am, and Cm, are located in group VIA, under W."

Sidgwick writes:

"This subgroup (VIA) consists of Cr, Mo, W, and U, to which the 'uranide' elements, Np, Pu, Am, and Cm (which might be assigned to any Group from III to VI) must now be added." (p. 998)

"...the trans-uranium elements 93–6... for the first time give clear evidence of the opening of the 'second rare earth series', the 'uranides', through the expansion of the fifth quantum group from 18 towards 32." (p. 1069)

"The question whether the fifth quantum group of electrons which is completed up to 18 in gold begins to expand towards 32, as the fourth does in cerium, has now been settled by the chemical properties of these newly discovered elements. In the Ln the beginning of the expansion is marked by the main valency becoming and remaining 3. With these later elements of the seventh period there is scarcely any sign of valencies other than those of the group until we come to uranium... Up to and including uranium, the group valency is always the stablest, but beyond this no further rise of valency occurs, such as we find in rhenium and osmium. Hence the point of departure of the new series of structures (corresponding to lanthanum in the first series) is obviously uranium, and the series should be called the uranides. (p. 1092):

McCutchon's Simplified Periodic Classification of the Elements

McCutchon KB, A simplified periodic classification of the elements, Journal of Chemical Education, vol. 27, no. 1, pp. 17–19 (1950)

This 3-dimensional table has two double-sided flaps attached. The top flap is the f bock. Under that is the d block.

The superscripts denote the number of d electrons an element has. Thus, La¹ is shown as being an f¹ element. But it has a 1 superscript, meaning that the f electron count is reduced by 1 and the d electron count is 1.

René Vernon writes:

"On group 3, McCutchon cryptically says: The proposed arrangement brings out certain known facts about the tertiary elements which are rarely shown by other arrangements. For example, it suggests, correctly, that the resemblance between yttrium and lutecium is greater than that between yttrium and lanthanum. It classifies lanthanum but not lutecium as a rare earth, in accordance with their chemical properties (which also contradict spectrographic evidence at this point). It also demonstrates the tetravalence of both cerium and thorium, and that thorium and protactinium show a resemblance in chemical properties to zirconium and niobium, as well as to hafnium and tantalum."

I say "cryptically" because McCutchon presents no further evidence in support of his assertion that the resemblance between Y and Lu is greater than between Y and La. He may have had in mind the fact that Lu is more often found in ores of Y than is the case for La... and I don't understand his reference to spectrographic evidence.

© Mark R. Leach Ph.D. 1999 –

Queries, Suggestions, Bugs, Errors, Typos...

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