Periodic Laws

F. P. Venable, The Developmeni of ihe Periodic Law, Chemical Publishing Co., Easton. Pa., 1896. This i.s Ihe first general review of periodic tables and has an almost complete colleclion of those published to that lime. J. W. Van Spronsen. The Periodic Syeiem of ihe Chemical Elements, Elsevier. Amsterdam, 1969, 368 pp. An excellent modem account of the historical developments leading up to Mendeleev s table. 

D. 1. Menddeev enunciated his periodic law that the properties of the elements are a periodic function of their... 

W, Pt, Au and the noble gases, though 0x0 compounds of all elements are known except for He, Ne, Ar and possibly Kr. This great range of compounds was one of the reasons why Mendeleev chose oxides to exemplify his periodic law (p. 20) and why oxygen was chosen as the standard element for the atomic weight scale in the early days when atomic weights were determined mainly by chemical stoichiometry (p. 16). 

One of the most fundamental principles of chemistry is the periodic law, which states that... 

Figure 8. Alternative and updated periodic table, adapted from tables developed by Thomas Bay ley, Jurgen Thomsen and Niels Bohn These tables all depict the symmetrical nature of the periodic law regarding the increase in intervals before periodicity occurs in every other period with the exception of the first one. Tie lines denote chemical analogies.

After spending considerable time perusing the crumbling pages of late nineteenth-century chemistry journals and textbooks, I have confirmed the traditional account Mendeleev s periodic law attracted little attention. . . until chemists started to discover some of the elements needed to fill the gaps in his table and found that their properties were remarkably similar to those he had predicted. The frequency with which the periodic law was mentioned in-journals increased sharply after the discovery of gallium, most of that increase was clearly associated with Mendeleev s prediction of the properties of the new element, (p, 617)20... 

While chemists differed on the relative importance of prediction and accommodation, it seems fair to approximate the consensus as follows. The reasons for accepting the periodic law are, in order of importance, [1] it accurately describes the correlation between physicochemical properties and atomic weights of nearly all known elements ... 

The reason why the predicted elements were less important to chemists than the known elements that were initially correlated by the periodic law is the same reason why they had not been discovered before 1869 their abundance at the earth s surface is very small, (p. 612)... 

If this is a correct analysis of it, then the chief problem with Brush s overall account—aside from any issue about the historical evidence in its favour—is that, by agreeing with Maher and Lipton that the novel predictions counted more while denying that they counted sufficiently more to outweigh the total effect of the accommodations, it ends up in no man s land. Brush may have an explanation for why special attention should have been paid to the predictive successes (they carried a lot of impact per unit , as it were) but this does not, despite his claims and despite, perhaps, first appearances, translate into an explanation for what he accepts is the historical fact that Mendeleev s periodic law attracted little attention before 1874—that is, before the initial success of the predictions. What his account would lead us to expect is, on the contrary, a high rate of credit for, and interest in, Mendeleev s scheme before 1874 and a somewhat higher rate afterwards. 

Remarkably enough, Brush immediately adds to this claim the admission that in many cases it is difficult to prove a causal relation [between the success of the predictions and the frequency with which the periodic law is mentioned] since the authors do not mention the prediction ibid.). Two points should be made ... 

And, indeed, Brush s evidence on this issue (given in his table 1) is striking no less than 132 of the 197 journal articles mentioning the periodic law in the period 1871-1890 fail to mention the confirmed predictions of new elements. 

The number of explicit references to the periodic law to be found in late nineteenth-century journals is small and fluctuates irregularly. From these data alone it would be difficult to judge whether the periodic law was actually accepted by the entire chemical community or was merely an exotic concept, of interest only to a few specialists, (p, 600)... 

If a majority of chemistry textbooks published in a country present the periodic law— as is the case for the United States and Britain by 1890—it is reasonable to conclude that the law was generally accepted in that country, (ibid,)21... 

Perhaps the two most striking passages quoted by Brush are from William Crookes and from Mendeleev himself Brush claims that the latter stressed the importance of predictions when he reviewed the status of his periodic law in 1879 (ibid.) in the following remark (to which we have added the emphasis) ... 

The rows and columns of Mendeleev s table are meant to reflect the periodic function asserted to exist by this periodic law. 

It is no surprise that Mendeleev never gave precise mathematical expression to this periodic function . In fact, it would be impossible, we claim, to state at all precisely the content of Mendeleev s periodic law . (We are, of course, referring here to the law as articulated by Mendeleev himself and as understood by his contemporaries. There is no doubt that the subsequent development of chemistry has seen at least great progress toward the articulation of a precise version of the periodic law, based ultimately on quantum mechanics.24)... 

Mendeleev clearly believed (along with others) that there is a whole set of dependencies of chemical properties on atomic weight and that some of these properties recur at regular intervals. The periodic law amounts, essentially, to a commitment to look for such dependencies and recurrences, and the suggestion that something of importance will emerge from this search. 

Notice that the lack of specificity of the periodic law as then conceived does not entail that Mendeleev failed to operate in a precise way locally. For example, he himself gave a clear account of his approach to working out some of the main relationships between the properties of the elements in his textbook The Principles of Chemistry. The method consists of simultaneous interpolation within groups or columns as well as within periods or rows of the periodic table. The average of the values of the numerical properties of the four elements flanking the element in question are taken to determine the latter s properties. So Mendeleev wrote ... 

See Scerri (1998), where it is argued that, while still no one has succeeded in giving a mathematically precise version of the periodic law, and while the law has not exactly been reduced to quantum mechanics, sufficient progress has been made to suggest that a precise version of the law may eventually be possible (if only in the limit ). (See also Scerri, 1999, where further clarification is provided.)... 

This was extremely important for [Ramsay] as an affirmation of the position of the newly discovered elements, and for me as a glorious confirmation of the general applicability of the periodic law.27... 

Mendeleev, D, I. (1879a) The Periodic Law of the Chemical Elements , The Chemical News and Journal of Physical Science 40, 78-79. 

Mendeleev, D, I. (1958) Periodicheskii Zakon, Osnovye Statl, Compilation and Commentary of articles on the periodic law by B. M. Kedrov, Klassiki Nauki, Ac.Sc. (Leningrad). 

Ovstrovsky, V.N., How and What Physics Contributes to Understanding the Periodic Law, Foundations of Chemistry, 2001 3 145-182,... 

The central idea that aided me in undertaking the study of the periodic law of the elements, consists primarily in the absolute distinction between an atom [of e.g. the element carbon] and a simple body [such as diamond or graphite] ([32, p 193]). 

Bent, H. A. New Ideas in Chemistry from Fresh Energy for the Periodic Law AuthorHouse Bloomington, IN, 2006. 

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