Henry Moseley, X-ray spectroscopy and the periodic table

2020 ◽  
Vol 378 (2180) ◽  
pp. 20190302 ◽  
Author(s):  
Russell G. Egdell ◽  
Elizabeth Bruton
Keyword(s):  
Periodic Table ◽  
Chemical Elements ◽  
Atomic Weight ◽  
X Rays ◽  
Radioactive Elements ◽  
Theme Issue ◽  
X Ray ◽  
Series Of Experiments ◽  
Radiological Characterization

Just over 100 years ago, Henry Moseley carried out a systematic series of experiments which showed that the frequencies of the X-rays emitted from an elemental target under bombardment by cathode rays were characteristic of that element and could be used to identify the charge on its atomic nucleus. This led to a reorganization of the periodic table, with chemical elements now arranged on the basis of atomic number Z rather than atomic weight A, as had been the case in previous tables, including those developed by Mendeleev. Moseley also showed that there were four ‘missing elements’ before gold. With further measurements up to uranium Z = 92, the Swedish physicist Manne Siegbahn identified two more missing elements. This paper provides an introduction to Moseley and his experiments and then traces attempts to ‘discover’ missing elements by X-ray spectroscopy. There were two successes with hafnium (Z = 72) and rhenium (Z = 75), but many blind alleys and episodes of self-deception when dealing with elements 43, 61, 85 and 87. These all turned out to be radioactive, with extremely small natural abundances: all required synthesis by a nuclear reaction, with radiological characterization in the first instance. Finally, the paper moves on to consider the role of X-ray spectroscopy in exploring the periodic table beyond uranium. Although the discovery of artificial radioactive elements with Z > 92 again depended on nucleosynthesis and radiological characterization, measurement of the frequencies or energies of characteristic X-rays remains the ultimate goal in proving the existence of an element. This article is part of the theme issue ‘Mendeleev and the periodic table’.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

scholarly journals IUPAC Periodic Table Challenge

2020 ◽  
Vol 42 (2) ◽  
pp. 18-21
Author(s):  
Juris Meija ◽  
Javier Garcia-Martinez ◽  
Jan Apotheker
Keyword(s):  
General Public ◽  
Periodic Table ◽  
Chemical Elements ◽  
Global Competition ◽  
Daily Lives ◽  
The World

AbstractIn 2019, the world celebrated the International Year of the Periodic Table of Chemical Elements (IYPT2019) and the IUPAC centenary. This happy coincidence offered a unique opportunity to reflect on the value and work that is carried out by IUPAC in a range of activities, including chemistry awareness, appreciation, and education. Although IUPAC curates the Periodic Table and oversees regular additions and changes, this icon of science belongs to the world. With this in mind, we wanted to create an opportunity for students and the general public to participate in this global celebration. The objective was to create an online global competition centered on the Periodic Table and IUPAC to raise awareness of the importance of chemistry in our daily lives, the richness of the chemical elements, and the key role of IUPAC in promoting chemistry worldwide. The Periodic Table Challenge was the result of this effort.

scholarly journals Role of the periodic table in discovery of new elements

2011 ◽  
Vol 1 (1) ◽  
pp. 1-5 ◽  
Author(s):  
D.C. Hoffman
Keyword(s):  
Periodic Table ◽  
Predictive Power ◽  
Chemical Elements ◽  
Chemical Properties ◽  
Negative Effects ◽  
Current Form ◽  
Future Role ◽  
History Of ◽  
Chemical Techniques

AbstractThis year (2009) marks the 140th Anniversary of Mendeleev's original 1869 periodic table of the elements based on atomic weights. It also marks the 175th anniversary of his birth in Tolbosk, Siberia. The history of the development of periodic tables of the chemical elements is briefly reviewed beginning with the presentation by Dmitri Mendeleev and his associate Nikolai Menshutkin of their original 1869 table based on atomic weights. The value, as well as the sometimes negative effects, of periodic tables in guiding the discovery of new elements based on their predicted chemical properties is assessed. It is noteworthy that the element with Z=101 (mendelevium) was identified in 1955 using chemical techniques. The discoverers proposed the name mendelevium to honor the predictive power of the Mendeleev Periodic Table. Mendelevium still remains the heaviest element to have been identified first by chemical rather than nuclear or physical techniques. The question concerning whether there will be a future role for the current form of the periodic table in predicting chemical properties and aid in the identification of elements beyond those currently known is considered.

scholarly journals FEATURES OF DENTINE CHEMICAL COMPOSITION OF INTACT TEETH AND TEETH WITH WEDGE-SHAPED DEFECTS

2021 ◽  
Vol 74 (8) ◽  
pp. 1869-1875
Author(s):  
Svitlana P. Yarova ◽  
Iryna I. Zabolotna ◽  
Olena S. Genzytska ◽  
Andrii A. Komlev
Keyword(s):  
Chemical Composition ◽  
Chemical Elements ◽  
Cervical Region ◽  
Cervical Lesions ◽  
X Ray ◽  
Sodium Magnesium ◽  
Calcium Phosphorus ◽  
Cervical Area ◽  
Focused Beam

The aim: Is to define dentine chemical composition of intact teeth and those with wedge-shaped defects followed by the analysis of revealed differences. Materials and methods: Longitudinal sections of 22 clinically removed teeth (12 – clinically intact ones, 10 – with wedge-shaped defects) from both jaws were studied in patients aged between 25-54 years. JSM-6490 LV focused beam electron microscope (scanning) with system of energy-dispersive X-ray microanalysis INCA Penta FETх3 was used. The chemical composition of 148 dentine areas in the incisal region (tubercle), equator, cervical area has been determined as a percentage of the weight amounts of carbon, oxygen, calcium, phosphorus, sodium, magnesium, sulfur, chlorine, zinc, potassium, aluminum. Results: Dentine chemical composition of teeth with wedge-shaped defects differed from those of intact teeth by significantly lower content: sodium, chlorine and calcium – in the incisal region (tubercle); sodium, magnesium − at the equator; sodium, chlorine and calcium – in the cervical region (p≤0.05). In the sample groups with cervical pathology there was more sulfur and oxygen in the incisal region (tubercle), phosphorus and zinc – at the equator, carbon and potassium – in the cervical region (p≤0.05). Conclusions: Differences in the chemical composition of intact teeth and teeth with wedge-shaped defects, the presence of correlation between the studied chemical elements confirm the role of macro- and microelements in the pathogenesis of non-carious cervical lesions.

HYPOTHESIS ON THE SYNERGISM OF RADIATION AND WATER FILTERS IN THE FORMATION OF BIOOBJECTS

2019 ◽  
Vol 21 (1) ◽  
pp. 53-58
Author(s):  
B.L. Oksengendler ◽  
S.E. Maksimov ◽  
S.U. Norbaev ◽  
L.Yu. Akopyan ◽  
M.V. Konoplyova ◽  
...  
Keyword(s):  
Periodic Table ◽  
Chemical Elements ◽  
Electron Shell ◽  
Living Matter ◽  
Heavy Atoms ◽  
The Third ◽  
Water Filters ◽  
Selection Of ◽  
Electron Shells

The article contains a hypothesis on the dominance of chemical elements of top periods of the Periodic Table in living matter. The idea is that the elements of the third and next periods of the table, in contrast to the first two periods, have larger number of subvalent electron shells. Because of this, ionization of the k-electron shell by radiation (kosmic and terrestrial) in the heavy atoms always leads to the Auger cascade, which causes the destruction of molecular chains. This mechanism can play a role of the radiation filter in the selection of light chemical elements in living matter in addition to the mechanism of hydrolytic filter (G.R. Ivanitskii).

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 Metals and non-metals in the periodic table

2020 ◽  
Vol 378 (2180) ◽  
pp. 20200213
Author(s):  
Benzhen Yao ◽  
Vladimir L. Kuznetsov ◽  
Tiancun Xiao ◽  
Daniel R. Slocombe ◽  
C. N. R. Rao ◽  
...  
Keyword(s):  
Periodic Table ◽  
Chemical Elements ◽  
Quantum Mechanical ◽  
Great Success ◽  
Ambient Conditions ◽  
Theme Issue ◽  
Atomic Properties ◽  
System A ◽  
Mechanical Approach ◽  
Quantum Mechanical Approach

The demarcation of the chemical elements into metals and non-metals dates back to the dawn of Dmitri Mendeleev's construction of the periodic table; it still represents the cornerstone of our view of modern chemistry. In this contribution, a particular emphasis will be attached to the question ‘Why do the chemical elements of the periodic table exist either as metals or non-metals under ambient conditions?’ This is perhaps most apparent in the p-block of the periodic table where one sees an almost-diagonal line separating metals and non-metals. The first searching, quantum-mechanical considerations of this question were put forward by Hund in 1934. Interestingly, the very first discussion of the problem—in fact, a pre-quantum-mechanical approach—was made earlier, by Goldhammer in 1913 and Herzfeld in 1927. Their simple rationalization, in terms of atomic properties which confer metallic or non-metallic status to elements across the periodic table, leads to what is commonly called the Goldhammer–Herzfeld criterion for metallization. For a variety of undoubtedly complex reasons, the Goldhammer–Herzfeld theory lay dormant for close to half a century. However, since that time the criterion has been repeatedly applied, with great success, to many systems and materials exhibiting non-metal to metal transitions in order to predict, and understand, the precise conditions for metallization. Here, we review the application of Goldhammer–Herzfeld theory to the question of the metallic versus non-metallic status of chemical elements within the periodic system. A link between that theory and the work of Sir Nevill Mott on the metal-non-metal transition is also highlighted. The application of the ‘simple’, but highly effective Goldhammer–Herzfeld and Mott criteria, reveal when a chemical element of the periodic table will behave as a metal, and when it will behave as a non-metal. The success of these different, but converging approaches, lends weight to the idea of a simple, universal criterion for rationalizing the instantly-recognizable structure of the periodic table where … the metals are here, the non-metals are there … The challenge of the metallic and non-metallic states of oxides is also briefly introduced. This article is part of the theme issue ‘Mendeleev and the periodic table’.

The Discovery of X-Rays: a Probable Case of Second Order Observation

2018 ◽  
Vol 19 (4) ◽  
pp. 403
Author(s):  
Marco Aurélio Clemente Gonçalves ◽  
Mariele Regina Pinheiro Gonçalves ◽  
Pablo Eduardo Ortiz
Keyword(s):  
History Of Science ◽  
Second Order ◽  
Point Of View ◽  
X Rays ◽  
Historical Reconstruction ◽  
X Ray ◽  
Probable Case ◽  
The Status ◽  
History Of

The discovery of x-rays, one of the most beautiful experiments ever carried out, generates numerous controversies and these, in turn, can trigger a series of counterproductive information regarding not only the History of Science but also the teaching  activity. The aim of this article is to resolve these controversies concerning what ocurred and highlight the important role of the German physicist Wilhelm Conrad Röntgen, highlighting not only his genius but, especially in this case in particular, his condition of second-order observer. It is not uncommon to find information in various media refering to this discovery under the claim that it was the result of a fortuitous event, and this denotes a profound lack of knowledge about the facts or a disrespect for the renowned discoverer. Such allegations about the event depreciate the extraordinary discovery that impacts humanity, from the deed  to the present. Thus, through a brief historical reconstruction, it was tried to present here what had happened judiciously. With this respect, the brilliant scientist is given the status of a second-rate observer, from the philosophical point of view. This condition resonates with the diachronic aspect of the History of Science, according to the perspective presented here, and it is also supported by the time taken by the discoverer from the beginning of his research until the end of it. Keywords: X-Ray. Second-Order Observer. History of Science. ResumoO descobrimento dos raios-x, um dos mais belos experimentos já realizados, gera inúmeras controvérsias e essas, por sua vez, podem desencadear uma série de informações contraproducentes no tangente não só a História da Ciência como também à atividade de ensino. O presente artigo tem como objetivo dirimir tais polêmicas com respeito ao ocorrido e destacar o importante papel do físico alemão Wilhelm Conrad Röntgen, destacando não só sua genialidade, mas sobretudo, neste caso em particular, a sua condição de observador de segunda ordem. Não é raro encontrar em diversos meios de comunicação informações com respeito a referida descoberta sob a alegação de que a mesma fora fruto de um caso fortuito e isso denota profundo desconhecimento sobre os fatos, ou então, desrespeito com o renomado descobridor. Tais alegações sobre o sucedido depreciam a descoberta extraordinária que impacta a humanidade, desde o feito até a atualidade. Assim, através de breve reconstrução histórica, buscou-se aqui apresentar o ocorrido criteriosamente. Com este respeito passa-se a atribuir ao brilhante cientista a condição de observador de segunda ordem, do ponto de vista filosófico. Tal condição encontra ressonância no aspecto diacrônico da História da Ciência, segundo a perspectiva aqui apresentada e está amparada, também, pelo tempo empreendido pelo descobridor desde o início de sua pesquisa até a finalização da mesma. Palavras-chave: Raios-x. Observador de Segunda Ordem. História da Ciência.

Address of the President Sir Robert Robinson, at the Anniversary Meeting, 30 November 1949

1950 ◽  
Vol 201 (1064) ◽  
pp. 1-17
Keyword(s):  
Classical Tradition ◽  
Atomic Number ◽  
Atomic Weight ◽  
Optical Spectra ◽  
Radioactive Elements ◽  
X Ray ◽  
Close Analogue

The Copley Medal is awarded to Professor George Charles DE Hevesy, For. Mem. R. S., for his distinguished work on the chemistry of radioactive elements and especially for his use of isotopes as tracers in the study of biochemical problems. Hevesy was one of the last to join the distinguished company of discoverers of elements in the classical tradition. In 1923, in collaboration with Coster, he established the occurrence of the element with atomic number 72 in zirconia minerals, and called it hafnium. This was shown to be a close analogue and constant comparison of zirconium, but a method of separation by chemical means was devised. The atomic weight was found to be 178.6, and the X-ray and optical spectra were fully described.

scholarly journals Bakerian Lecture: Nuclear constitution of atoms

1920 ◽  
Vol 97 (686) ◽  
pp. 374-400 ◽  
Keyword(s):  
Large Mass ◽  
Atomic Weight ◽  
Single Atom ◽  
Central Field ◽  
X Rays ◽  
Hyperbolic Orbit ◽  
Series Of Experiments ◽  
Charged Nucleus ◽  
Positively Charged ◽  
Α Particles

Introduction .—The conception of the nuclear constitution of atoms arose initially from attempts to account for the scattering of α-particles through large angles in traversing thin sheets of matter. Taking into account the large mass and velocity of the α-particles, these large deflexions were very remarkable, and indicated that very intense electric or magnetic fields exist within the atom. To account for these results, it was found necessary to assume that the atom consists of a charged massive nucleus of dimensions very small compared with the ordinarily accepted magnitude of the diameter of the atom. This positively charged nucleus contains most of the mass of the atom, and is surrounded at a distance by a distribution of negative electrons equal in number to the resultant positive charge on the nucleus. Under these conditions, a very intense electric field exists close to the nucleus, and the large deflexion of the α-particle in an encounter with a single atom happens when the particle passes close to the nucleus. Assuming that the electric forces between the α-particle and the nucleus varied according to an inverse square law in the region close to the nucleus, the writer worked out the relations connecting the number of α-particles scattered through any angle with the charge on the nucleus and the energy of the α-particle. Under the central field of force, the α-particle describes a hyperbolic orbit round the nucleus, and the magnitude of the deflection depends on the closeness of approach to the nucleus. From the data of scattering of α-particles then available, it was deduced that the resultant charge on the nucleus was about ½ A e , where A is the atomic weight and e the fundamental unit of charge. Geiger and Marsden made an elaborate series of experiments to test the correctness of the theory, and confirmed the main conclusions. They found the nucleus charge was about ½ A e , but, from the nature of the experiments, it was difficult to fix the actual value within about 20 per cent. C. G. Darwin worked out completely the deflexion of the α-particle and of the nucleus, taking into account the mass of the latter, and showed that the scattering experiments of Geiger and Marsden could not be reconciled with any law of central force, except the inverse square. The nuclear constitution of the atom was thus very strongly supported by the experiments on scattering of α-rays. Since the atom is electrically neutral, the number of external electrons surrounding the nucleus must be equal to the number of units of resultant charge on the nucleus. It should be noted that, from the consideration of the scattering of X-rays by light elements, Barkla had shown, in 1911, that the number of electrons was equal to about half the atomic weight. This was deduced from the theory of scattering of Sir J. J. Thomson, in which it was assumed that each of the external electrons in an atom acted as an independent scattering unit.

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