Element 72—Hafnium

2013 ◽  
Author(s):  
Eric Scerri
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Periodic System ◽  
Periodic Table ◽  
Atomic Weight ◽  
The Other ◽  
Niels Bohr ◽  
General Consensus ◽  
The University ◽  
Missing Element

The story concerning the discovery and isolation of element 72 bears all the characteristics of controversy and nationalistic overtones that seems to characterize many of our seven elements. On one hand, it seems odd that there should be so much controversy associated with these elements given that Moseley’s method had apparently provided an unequivocal means through which elements could be identified as well as a way of knowing just how many elements remained to be discovered. On the other hand, perhaps it was precisely because the problem of the missing elements became so clearly focused on a few elements, with known atomic numbers, that the stakes became higher than they would have been if the number of elements remaining to be discovered had been uncertain, as they were in pre-Moseley times. Element 72 (fig. 4.1) was clearly anticipated, although not as such, even in Mendeleev’s earliest table of 1869. As fig. 4.2 shows, Mendeleev considered that an as yet undiscovered element with an atomic weight of 180 should be a homologue of zirconium (The modern accepted value is 178.50). This fact may not seem very significant and yet we will see, as the story of this chapter unfolds, that it amounts to Mendeleev predicting that this element would be a transition metal rather than a rare earth. But Mendeleev was not really in a position to make such a statement since the nature and number of rare earth elements was unknown in his day. Indeed, the problem of the rare earths was one of the most acute challenges to his periodic system and one that he personally never resolved. Sometime later, Julius Thomsen, a chemistry professor at the University of Copenhagen and incidentally the chemistry instructor to the physicist Niels Bohr, published a periodic table in which he too included a missing element that was a homologue of zirconium (fi g. 4.3). Suffice it to say that there was a general consensus among chemists that on the basis of the periodic table there should exist an element before tantalum that would be a homologue of zirconium.

Element 61—Promethium

2013 ◽  
Author(s):  
Eric Scerri
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Periodic System ◽  
Periodic Table ◽  
The Other ◽  
Great War ◽  
X Ray ◽  
The Great War

The last of our seven elements to be isolated was element 61, which is also the only rare earth among the seven. The problem with rare earths, which are 15 or even 17 in number depending on precisely how they are counted, is that they are extremely similar to each other and as a result are very difficult to separate. When the periodic table was first discovered in the 1860s only two or three rare earths even existed. As more of them turned up it became increasingly difficult to place them in the periodic system. Just like with all the other seven elements in our story, there were many false claims to its discovery. Moreover, the early claims must have seemed very plausible at the time because they appeared to draw support from X-ray evidence and Moseley’s law. Just like the priority dispute involving hafnium that took place in the early 1920s, the case of element 61 also involved an international controversy. This time one cannot entirely blame the aftermath of the Great War, as the two opponents consisted of Italians and Americans, with much of the scientific chicanery taking place, as was usual for the time, in the pages of London’s Nature magazine. But even though both sides of the priority dispute appealed to X-ray data and Moseley’s law, it turned out that neither side was right. In their own way, each side was working in complete delusion, since element 61 is highly radioactive and unstable, does not occur naturally on Earth, and could only be isolated in minute quantities by artificial means when such methods became sufficiently developed in the 1940s. Let us start at the beginning. In 1902, the Bohemian rare earth chemist Bohuslav Brauner was the first to suggest that an element lying precisely between neodymium and samarium remained to be discovered. He gave talks in his native Bohemia and published articles in some fairly obscure journals, all of which meant that few chemists in the wider arena became aware of his work.

scholarly journals The isotopic constitution and atomic weights of hafnium, thorium, rhodium, titanium, zirconium, calcium, gallium, silver, carbon, nickel, cadmium, iron and indium

1935 ◽  
Vol 149 (867) ◽  
pp. 396-405 ◽  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Rare Earths ◽  
Mass Spectra ◽  
Mass Number ◽  
Atomic Weight ◽  
Complete Data ◽  
Pure Sample ◽  
Titanium Zirconium ◽  
Similar Element

An account of experiments has already been given by which the analyses of the rare earth elements were completed with the aid of a particularly favourable arrangement of the anode ray apparatus. This paper contains a description of analyses of other elements made with the same setting and also of some others subsequently made to obtain more accurate and complete data on elements whose constitution had already been provisionally settled. Results (72) Hafnium —Many previous attempts to obtain the mass spectra of this element had failed. For the most similar element, zirconium, the only successful results had been obtained from the fluoride. A pure sample of hafnium fluoride had been kindly provided by Professor G. v. Hevesy, one of the discoverers of the element, and this was incorporated into the anode mixture. The first trial was a failure; but after the work on zirconium described below a second attempt was made, this time with resolved, so that only rough estimates of abundance could be obtained. These were as follows:— Mass numbers . . . . . 176 177 178 179 180 % abundance . . . . . . 5 19 28 18 30 These given a mean mass number 178·5. Applying the same correction as with the rare earths we get atomic weight of hafnium = 178·4 ± 0·2 in fair agreement with the International value 178·6.

The Seven Last Infra-Uranium Elements to Be Discovered

2019 ◽  
Author(s):  
Eric Scerri
Keyword(s):  
Periodic Table ◽  
Atomic Weight ◽  
Weak Acid ◽  
Ray Method ◽  
Natural Sources ◽  
Transuranium Elements ◽  
X Ray ◽  
Naturally Occurring ◽  
Missing Element

The term “infra-uranium,” meaning before uranium, is one that I have proposed by contrast to the better-known term transuranium elements that are discussed in the following chapter. The present chapter concerns the last seven elements that formed the missing gaps in the old periodic table that ended with the element uranium. After Moseley developed his X-ray method, it became clear that there were just seven elements yet to be isolated among the 92 naturally occurring elements or hydrogen (#1) to uranium (#92). This apparent simplicity is somewhat spoiled by the fact that, as it turned out, some of these seven elements were first isolated from natural sources following their being artificially created, but this raises more issues that are best left to the next chapter of this book. The fact remains that five of these seven elements are radioactive, the two exceptions being hafnium and rhenium, the second and third of them to be isolated. The first of the seven final infra-uranium elements to be discovered was protactinium, and it was one of the lesser-known predictions made by Mendeleev. In his famous 1896 paper, Mendeleev indicated incorrect values for both thorium (118) and uranium (116). (See figure 1.6.) A couple of years later, he corrected both of these values and showed a missing element between thorium and uranium (figure 4.4). In doing so, Mendeleev added the following paragraph, in which he made some specific predictions. . . . Between thorium and uranium in this series we can further expect an element with an atomic weight of about 235. This element should form a highest oxide R2O5, like Nb and Ta to which it should be analogous. Perhaps in the minerals which contain these elements a certain amount of weak acid formed from this metal will also be found.. . . The modern atomic weight for eka-tantalum or protactinium is 229.2. The apparent inaccuracy in Mendeleev’s prediction is not too surprising, however, since he never knew that protactinium is a member of only four “pair reversals” in the entire periodic table.

scholarly journals The isotopic constitution and atomic weights of the rare earth elements

1934 ◽  
Vol 146 (856) ◽  
pp. 46-55 ◽  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Positive Result ◽  
Rare Earths ◽  
Periodic Table ◽  
Resolving Power ◽  
Fundamental Importance ◽  
Lack Of Information ◽  
Isotopic Constitution ◽  
The Rare Earth

Hitherto the widest gap in our knowledge of the isotopic constitution of the elements has been in that part of the periodic Table containing rare earths. A means of obtaining the mass rays of these substances was discovered 10 years ago. By this it was possible to demonstrate the simplicity of lanthanum and praseodymium and to obtain a provisional analysis of the complex elements cerium and neodymium. Beyond these the only positive result was a faint blurr which suggested that erbium was complex and it was decided to postpone further attempts until an instrument of higher resolving power was available. When this was constructed it was naturally first applied to the numerous problems which appeared to be of more fundamental importance so that the complete lack of information on elements 62 to 76 remained.

Prediction and Accommodation: The Acceptance of Mendeleev’s Periodic System

2019 ◽  
Author(s):  
Eric Scerri
Keyword(s):  
Periodic System ◽  
Periodic Table ◽  
Scientific Community ◽  
The Other ◽  
Periodic Systems ◽  
Scientific Theories ◽  
Scientific Culture ◽  
System P ◽  
History Of ◽  
The One

Although periodic systems were produced independently by six codiscoverers in the space of a decade, Dmitri Mendeleev’s system is the one that has had the greatest impact by far. Not only was Mendeleev’s system more complete than the others, but he also worked much harder and longer for its acceptance. He also went much further than the other codiscoverers in publicly demonstrating the validity of his system by using it to predict the existence of a number of hitherto unknown elements. According to the popular story, it was Mendeleev’s many successful predictions that were directly responsible for the widespread acceptance of the periodic system, while his competitors either failed to make predictions or did so in a rather feeble manner. Several of his predictions were indeed widely celebrated, especially those of the elements germanium, gallium, and scandium, and many historians have argued that it was such spectacular feats that assured the acceptance of Mendeleev’s periodic system by the scientific community. The notion that scientific theories are accepted primarily if they make successful predictions seems to be rather well ingrained into scientific culture, and the history of the periodic table has been one of the episodes through which this notion has been propagated. However, philosophers and some scientists have long debated the extent to which predictions influence the acceptance of scientific theories, and it is by no means a foregone conclusion that successful predictions are more telling than other factors. In looking closely at the bulk of Mendeleev’s predictions in this chapter, it becomes clear that, at best, only half of them proved to be correct. This raises a number of questions. First of all, why is it that history has been so kind to Mendeleev as a maker of predictions? As historian of chemistry William Brock has pointed out, “Not all of Mendeleev’s predictions had such a happy outcome; like astrologers’ failures, they are commonly forgotten.”

VIII. A critical study of spectral series.— Part III. The atomic weight term and its import in the constitution of spectra

1914 ◽  
Vol 213 (497-508) ◽  
pp. 323-420
Keyword(s):  
Periodic Table ◽  
Principal Series ◽  
Atomic Weight ◽  
The Other ◽  
Critical Study ◽  
Spectral Series ◽  
Present Communication ◽  
The Real ◽  
Real Relation ◽  
The One

The doublet and triplet separations in the spectra of elements are, as has long been known, roughly proportional to the squares of their atomic weights, at least whenelements of the same group of the periodic table are compared. In the formulæ which give the series lines these separations arise by certain terms being deducted from the denominator of the typical sequences. For instance, in the alkalies if the p -sequence be written N/D m 2 , where D m = m +μ+α/ m the p -sequence for the second principal series has denominator D—Δ, and we get converging doublets; whereas the constant separations for the S and D series are formed by taking S 1 (∞) = D 1 (∞) = N/D 1 2 and S 2 (∞) = D 2 (∞)= N/(D 1 —Δ) 2 . It is clear that the values of Δ for the various elements will also be roughly proportional to the squares of the atomic weights. For this reason it is convenient to refer to them as the atomic weight terms. We shall denote them by Δ in the case of doublets and Δ 1 and Δ 2 in the case of triplets, using v as before to denote the separations. Two questions naturally arise. On the one hand what is the real relation between them and the atomic weights, and on the other what relation have they to the constitution of the spectra themselves ? The present communication is an attempt to throw some light on both these problems.

The First Publication of Mendeleev’s Periodic System of Elements

2020 ◽  
Vol 50 (1-2) ◽  
pp. 129-182
Author(s):  
Petr A. Druzhinin
Keyword(s):  
Periodic System ◽  
Periodic Table ◽  
Atomic Weight ◽  
Historical Research ◽  
Publication Date ◽  
Chemical Affinity ◽  
Historical Archive ◽  
Russian State ◽  
History Of ◽  
Printed Materials

This study explores the full set of handwritten and printed materials associated with the 1869 publication of the first version of Dmitrii Mendeleev’s periodic system of elements: “An Attempt at a System of Elements Based on Their Atomic Weight and Chemical Affinity.” Using innovative historical research methods, the author has been able to refute the publication date traditionally associated with the first version of the periodic table, as well as to establish an accurate chronology of its subsequent publications. This task was made possible through the discovery of previously unknown handwritten materials in Mendeleev’s personal archive and the Russian State Historical Archive. This typographical analysis of the first publication of Mendeleev’s periodic table represents a rare and unusual opportunity in the history of science: it gives us the chance to observe how, in the process of publishing the results of a scientific study, a researcher comes to realize that what he has discovered is, in fact, a major scientific breakthrough and begins to take the necessary steps toward establishing his scientific priority.

Effect of atmosphere and rare earth on liquidus relations in RE–Ba–Cu Oxides

1989 ◽  
Vol 4 (4) ◽  
pp. 752-754 ◽  
Author(s):  
J. E. Ullman ◽  
R. W. McCallum ◽  
J. D. Verhoeven
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Rare Earths ◽  
Liquidus Surface ◽  
High Temperature Superconductors ◽  
Decomposition Temperature ◽  
The Other ◽  
Peritectic Decomposition ◽  
Invariant Points ◽  
Liquidus Temperatures

In the processing of the high temperature superconductors RE1Ba2Cu3O7−x a knowledge of the liquidus temperatures is required in order to avoid liquid formation during the initial reactions of the starting materials. We have investigated the invariant points on the liquidus surface of the RE–Ba–Cu–O systems for RE = Y, Er, Gd, and Nd in oxygen, air, and argon, While the temperatures of the low melting reactions are almost independent of the rare earth species, they are heavily dependent on oxygen partial pressure. In addition, the peritectic decomposition temperature of the REBa2Cu3O7 phase was found to be a function of rare earth with a significantly higher value for the Nd compound than for the other rare earths.

Quantitative Relationships among the Elements and the Origins of the Periodic Table

2019 ◽  
Author(s):  
Eric Scerri
Keyword(s):  
Periodic System ◽  
Periodic Table ◽  
Quantitative Data ◽  
Atomic Weight ◽  
Equivalent Weight ◽  
Crucial Importance ◽  
Chemical Substances ◽  
P Elements ◽  
Chemical Knowledge ◽  
Fundamental Physical

Elements within a vertical group on the periodic table share certain chemical similarities, but the modern periodic system is not derived purely from descriptive characteristics. If chemical similarities were the sole basis for their classification, there would be many cases where the order and placement of the elements would be ambiguous. The development of the modern periodic system began when it was recognized that there are precise numerical relationships among the elements. Its subsequent evolution has also involved contributions from physics, as described in subsequent chapters. But whereas the latter contributions drew on fundamental physical theories, the ones that are examined in this chapter do not share this aspect. Instead, they involved looking for patterns among the numerical properties, such as equivalent weight or atomic weight, associated with each element. Throughout its history, the development of the periodic table has required a delicate interplay between two contrasting approaches: discerning quantitative physical data, on one hand, and observing qualitative similarities among the elements as a form of natural history, on the other. Both approaches are essential, and the balance that has been struck between them has been of crucial importance at various stages in our story. Whereas attention to qualitative aspects has always been an essential part of chemistry, the use of quantitative data has been a relatively new addition. The time when chemists began to pay attention to quantitative aspects of chemical reactions and chemical substances has been the source of much debate among historians. The traditional view has been that this step was taken by Antoine Lavoisier , who is regarded as the founder of modern chemistry. The more recent historical account is that Lavoisier made few original contributions and that much of his fame lay in his abilities as an organizer and presenter of chemical knowledge. Nevertheless, Lavoisier was able to dispel some of the vagueness and confusion that dogged the field of chemistry as he found it.

Rare earths in some niobate-tantalates

1958 ◽  
Vol 31 (240) ◽  
pp. 763-780 ◽  
Author(s):  
J. R. Butler
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
The Other

SummaryRare-earth distribution has been determined for fourteen niobatetantalates containing essential rare earths. Those minerals with more than about 15 % TiO2 (and corresponding to either priorites or members of the euxenite-polycrase series) have Yt as the dominant rare earth with the heavier lanthanons in excess of the lighter lanthanons. Those minerals with less than about 4 % TiO2 and less than about 30 % (Yt,Ln)2O3 (and corresponding to samarskites) also have Yt as the dominant rare earth but they show a marked concentration of Gd + Tb + Dy over the other lanthanons. It is tentatively suggested that this power of selective lanthanon enrichment may be characteristic of samarskite among the niobate-tantalates examined.

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