Left-step table

This much is quite readily acceptable but proponents of the left-step table make an additional change to the conventional format by moving the element helium from the head of the noble gases to the head of the alkaline earths. Given my initial preference for purely... 

Paper eight first appeared in the Journal of Chemical Education in 2008. Whereas in my book on the periodic table, I recommended the left-step table as the best possible representation, I subsequently changed my mind and proposed a new table. First of all let me say why I initially supported the left-step table. My attention was first drawn to the left-step table by Henry Bent s unpublished booklets on the subject, although I felt that his... 

What actually converted me to the left-step table, at least for a period of a few years, was a rather concise paper by the periodic table designer Gary Katz, which appeared in The Chemical Educator.20 My own support for this form of the table centered on my interest in the dual sense of the term element and in particular the more fundamental sense, called element as a basic substance by Paneth. 

With all these advantages one might well wonder why the left-step table has not attracted more attention and indeed why it has not been widely adopted. The answer to this question lies in the placement of one crucial element, helium. In the left-step table, helium is placed among the alkaline earth metals as mentioned above. To most chemists this is completely abhorrent since helium is regarded as the noble gas par excellence. Meanwhile, to a physicist or somebody who emphasizes electronic properties, helium falls rather naturally into the alkaline earths since it has two outer-shell electrons. 

However, one aspect, having to do with triads of elements, is troubling in this otherwise elegant left-step periodic system. The use of the left-step table results in the loss of a triad involving helium, neon, and argon. 

As suggested in the title of the present article, we believe that the periodic table, which initially arose from the discovery of atomic weight triads, can now be further enhanced by recognizing the fundamental importance of atomic number triads. In addition one should recognize the more fundamental nature of the elements as basic substances rather than as simple substances, and that the periodic system is primarily a classification of the former. Whereas we previously suggested that these aims were best served by the left-step table we now favor the revised left-step table shown in Figure 3. 

The proposed new table retains most of the feature of the Janet left-step table but does not commit one to placing helium in the alkaline earths. The regular form of the table represents an advantage over the medium-long form and the closer connection with electron-shell filling that the left-step table offers is maintained with the small disadvantage that two values of n + i, namely I and 2, appear in the same first row. 

The main motivation for this layout is that it leads to the formation of a new perfect triad involving hydrogen. In addition, the perfect triad involving helium is retained, unlike in the left-step table, where it is lost But why... 

ABSTRACT This article concerns various foundational aspects of the periodic system of the elements. These issues include the dual nature of the concept of an "element" to include element as a "basic substance" and as a "simple substance." We will discuss the question of whether there is an optimal form of the periodic table, including whether the left-step table fulfils this role. We will also discuss the derivation or explanation of the [n + , n] or Madelung rule for electron-shell filling and whether indeed it is important to attempt to derive this rule from first principles. In particular, we examine the views of two chemists, Henry Bent and Eugen Schwarz, who have independently addressed many of these issues. 2008 Wiley Periodicals, Inc. Int J Quantum Chem 109 959-971, 2009... 

Key words elements periodic table Madelung rule left-step table... 

It should also be said that the reason why Bent and Weinhold devote such attention to the n + ( rule is that, as mentioned earlier, the rule is clearly represented on the left-step table, the form of the periodic table that they favor. In addition, as was mentioned, the authors believe that the best representation of the periodic system should be based on the electronic structure of the neutral atoms of all the elements and not on their macroscopic properties. 

But what does all this work have to do with the question of the interpretation of the concept of an "element" This issue is not explicitly addressed in the paper by Bent and Weinhold but has been addressed by Bent in his recent book, which is entirely devoted to the left-step table [6]. 

Figure B.2 The left-step table (LST) of the chemical elements.

In 1926, Goldschmidt demonstrated the analogies between the elements Th, Pa, U and the lanthanides on the basis of the observation that the volumes of Th and U showed the same contractions as the ions of the lanthanide series. Striking early examples of periodic tables in which actinium, thorium, protactinium, and uranium are considered as homologues of the rare earths lanthanum, cerium, praseodymium, and neodymium are the circular system and left-step table of Charles Janet (Janet, 1929). 

It should be noted that although for decennia lanthanum and actinium could be found below yttrium in most periodic tables, some authors have placed lutetium below yttrium in the past. For instance, in the periodic table of Werner (1905a,b), there is an open place below yttrium at the position where lutetium is expected, but it should be realized that at that time lutetium had not yet been discovered (this was in 1907). However, Werner did not consider lanthanum as a homologue of yttrium, because of the differences in chemical properties between these two elements. Also in the circular system of Janet (Figure 28), the left-step table of Janet (Figure 32) and in the periodic table of Bohr (Figure 21), lutetium was placed below yttrium. 

From this point onward, 1 concentrate on the left-step table, although both representations are equahy viable for what follows. 

One might wonder - which periodic table is best As impossible as unnecessary to say Best for what purpose (s) Location of the problem elements The left-Step Table. Discussion of horizontal trends in metal/non-metal character ... 

The Left-step Table. Discussion of the most familiar elements, with beginning students The Conventional [medium-long form] table [...] Graphic display of secondary kinships Neither table. Better is Mendeleev s Short Form . 

---