See the recent articles and letters to the editor about this issue in the October issue of Journal of Chemical Education.

eric scerri

http://arxiv.org/PS_cache/nucl-th/pdf/0610/0610097v1.pdf
http://arxiv.org/PS_cache/nucl-th/pdf/0511/0511050v1.pdf
http://arxiv.org/PS_cache/nucl-th/pdf/0311/0311098v3.pdf
http://arxiv.org/PS_cache/nucl-th/pdf/0310/0310033v1.pdf
http://arxiv.org/PS_cache/nucl-th/pdf/0303/0303001v1.pdf

Valery Tsimmerman.

Despite the idea of the tetrahedron, there was also a difference in our approach. Jess was happy to find out that if s,p,d,f blocks are separated, they could be presented in 3D as the tetrahedron. I tried to keep them connected and used the tie lines for that purpose, in order to preserve the continuity in regard to the Atomic Number Z. This has become known as ADOMAH Periodic Table. I tried to keep blocks connected also in 3D by using concept of the tetrahedral packing of spheres that led me 3D representation of the Aufbau process.

Earlier, I was also contacted by George Jelliss (UK), who also arranged the blocks similar to the ADOMAH PT in 1986, however, his representation also lacked the continuity in regard to Z.

In any case, all this points to one thing: The tetrahedral representation of the periodic system is objective and, therefore, superior to all other (subjective) representations ofthe periodic law.

Sorry, but I have to disagree with the author of the “Final Thought” above. There is the Perfect representation of the Periodic System indeed and it is presented at http://www.perfectperiodictable.com.

Valery Tsimmerman (Larry Z.).

In the actual depiction with balls only 60 give you the pairs of electrons, leading me to suspect that perhaps one can split the system up and start building up the tetrahedron from two ends, on legs perpendicular but not connected by any vertex. If you do this then all 120 balls are used, and there is no dead space in the figure.

In this kind of system element 120 is ‘the end’- no other elements are possible if the sum 9 relation fixes things. In any case nuclear forces stop helping by element 120 anyway, science fiction elements notwithstanding.

I suspect that there are other geometrical patternings that can be found within the figure when unusual elemental, ionic, or molecular properties are taken into account, or interactions with nuclear structure. Nature is nothing if it isn’t math-crazy.

See: > http://cfpm.org/~majordom/memetics/2000/3042.html

Jess Tauber

Update: At the requst of commenters, I’ll incude a few more periodic tables inexplicably left out of the original round up.

Eric Scerri just left Michelle (the author of the Nature Chemistry article) a nice note about his periodic table. It is rather easy on the eyes – more than I can say for many alternatives – I have some problems with it. Mainly the position of hydrogen. From my comment below:

He notes that it (his periodic table) creates another atomic number triad with fluorine and chlorine, but I don’t see that as a compelling reason to place it in the halogen family.

Chemically, we can think of hydrogen in 3 different ways. Without the electron, it is a proton – the fundamental unit of Bronsted acids. I’d argue this is the most common (most important?) chemical use of hydrogen as a player in reaction mechanisms.

With one electron, it is the hydrogen atom – a radical. Used almost exclusively in radical chemistry. Surely an important part of synthesis, but not nearly as prevalent as a protic acid.

With two electrons, it is the hydride ion. Really only seen as metal hydrides and as an organic hydride in a select few reactions (Cannizzaro). Much less common than protic acids or radical chemistry. Important, no doubt… just uncommon. When you think of hydrogen, the hydride is not your first choice for mode of reactivity.

Placing hydrogen in the halogen family implies a mode of reactivity more like fluorine than lithium. This is certainly not the case.

———————

Thanks for the comment but my placement of hydrogen is not based upon its obvious chemical reactions, otherwise placement in the halogens would indeed seem a little contrived.

The idea is to place the element as a ‘basic substance’ rather than as a simple substance. There has been a great deal of discussion on this topic in the philosophy of chemistry literature.

Mendeleev himself stressed that the periodic table was primarily a classification of the abstract elements not their properties as simple substances or as isolated elements. The periodic table is as much a classification of elements as they occur in compounds.

Elements as basic substances are not directly accessible to experimental data. Their characteristics must be inferred. Mendeleev did this by considering bonded elements as well as the isolated elements.

Some 50 years later, the characteristic of elements as basic substances was recognized as being atomic number by Fritz Paneth a prominent radiochemist who also provided the official IUPAC defninition for what constitutes an element and which stands to this day. An element is picked out by citing its atomic weight. This is a necessary and sufficient criterion.

When I proposed my periodic table with H in the halogens I was arguing in terms of atomic number triads. H, F and Cl form a new atomic number triad if H is placed in the halogens but not if it is left in its traditional place in group 1.

I claim that this placement is more fundamental than appealing to properties of H as a simple substance or even as a bonded element since it comes closest to the notion of element as basic or abstract substance since it deals with relationships between atomic numbers, the one criterion for defining elements as basic substances.

References to the literature available on request.

Here is one of the papers,

E. Scerri The Dual Sense of the Term “Element, Attempts to Derive the Madelung Rule and the Optimal Form of the Periodic Table, if any, International Journal of Quantum Chemistry, (2009), 109, 959-971.

eric scerri

The manner in which electron shells fill is governed by the empirical rule of n + l rather than an n rule.

I claim that the n + l rule has not yet been deduced from quantum mechanics and as a consequence the periodic table has not been fully explained.

The usually encountered textbook accounts of the periodic table imply that QM explains everything.

Any comments folks?

eric scerri “The Periodic Table, Its Story and Its Significance, OUP, 2007.