Alkaline earth elements helium

A set of squared overlaps is given in Table 1 for states of the alkaline earth elements and for two states of doubly-excited helium. This Table is taken from Batka and Berry [10], who in turn took the values for the CI-RV overlaps from Hunter and Berry [11]. The Table also includes the squares of the RV-HF overlaps so that one can see the similarity of the two zero-order functions. 

Both of these alternative representations of the periodic system display the elements in a continuous manner with no break between any sets of elements, contrary to what is encountered in the currently accepted medium-long form. But these tables also contain a feature that causes many chemists some concern, in that the element helium is firmly located among the alkaline earth elements. 

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... 

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. 

It occurred to me that if one concentrated on this more fundamental sense of the concept of element, then the fact that helium does not seem to have properties in common with the alkaline earths would not be sufficient reason for not placing it among these elements in the periodic table. As I have later described this position, it was a form of why not argument rather than a positive reason for why helium should be placed among the alkaline earths. 

Consequently, they maintain that some displays of the periodic system may, in truth, be superior to others. Whereas the conventionally displayed table, called the medium-long form, has many virtues, it places helium among the noble-gas elements. Some have argued that in spite of appearances, helium should in fact be placed el the head of group 2, the alkaline earth group, which includes beryllium, magnesium and calcium. Helium has two outer-shell electrons as do the elements in the alkaline earth group. 

Of course it is important to distinguish between the shape of the periodic table, which is admittedly a matter of choice or convention, from tables that actually place certain elements in different groups. The point is not whether one should favor a tabular form, in which periods end abruptly, over circular displays which emphasize the continuity of the sequence of the elements for example. The question is rather whether to favor a table that places the element helium among the noble gases, when compared with tables that place this element among the alkaline earths. The wider question is whether elemental classification is an objective matter of fact or whether it is a matter of convention. It is the question of whether helium, for example, has a natural kinship with the noble gases or with the alkaline earths. Or as philosophers of science are apt to say, it is the question of whether or not groups, or families of elements, represent natural kinds. 

In this article it will be argued that the classification of the elements is an objective feature of the world and not open to conventional choice and relativism. It will also be argued that the element helium belongs objectively and most naturally either to the alkaline earths or the noble gases regardless of whether such a question may be settled at present.8... 

The s-block includes group 1 (the alkali metals) and group 2 (the alkaline earth metals) plus hydrogen and helium. The element hydrogen is placed in group 1 for convenience (International Union of Pure and Applied Chemistry [lUPAC] 2011) due to its electron configuration (ns ) but it is not an alkali metal. 

In the paper in this section I have suggested a philosophical way of accepting the placement of helium among the alkaline earths that does not depend of chemical or indeed physical properties. If one returns to the insistence on the real elements , then the chemical and physical differences between helium and the alkaline earths should be considered... 

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