Radiochim. Acta 2019; 107(9–11): 767–769

Syed M. Qaim, Jens-Volker Kratz and Eric Simoni Editorial: 150 years of the of Chemical Elements https://doi.org/10.1515/ract-2019-9983 . Several were attempting to discern some distinct patterns in their physico-chemical proper- ties. In 1860 the first ever international confer- ence was held in Karlsruhe, , under the chair of 1 Introduction August Kekulé, with many pioneering chemists partici- pating, among them and Michael Faraday. On the recommendation of the United Nations General The main aim of the conference was to establish stand- Assembly and the specific resolve of the United Nations ardisation methods in chemistry. During this conference Educational, Scientific and Cultural Organisation the famous Italian Stanislav Cannizzaro deliv- (UNESCO), the year 2019 was declared as the International ered a masterly lecture, as a result of which the chemistry Year of the Periodic Table of Chemical Elements (IYPT community adopted a unified system of atomic masses. 2019). This decision was based on a strong appreciation of This turned out to be a crucial step towards establishing international character of scientific cooperation pursued the periodic system. At that conference a young Russian in several frontier areas of basic and applied sciences chemist named was also present, having related to the Periodic Table. It should commemorate the come to Germany in 1859 on a 2-year state stipend to work 150th anniversary of the creation of that Table. As expected, under guidance of Robert Bunsen and at the decision was hailed with great enthusiasm by a large the University of Heidelberg. After his return to St. Peters- number of national, regional and international chemi- burg in , Mendeleev conjectured an arrangement of cal societies and other scientific organisations. The IYPT the then known 63 elements and presented a draft table, was officially launched on 29 January 2019 at the UNESCO based on atomic masses, in March 1869 to the Russian headquarters in Paris, France. Since then different types Chemical Society. A year earlier, i. e. in 1868, the German of functions, e. g. conferences, symposia, popular lec- chemist Lothar Meyer had written down a very similar tures, exhibitions and social gatherings, etc. have been periodic system of elements. In the following years the going on around the world, with the aim to increase the two tables had to undergo severe tests. For a long time the public awareness of in general, and chemistry in priority dispute between Meyer and Mendeleev remained. particular. Furthermore, a large number of journals are In recognition of their works, they were jointly awarded publishing editorials, commentaries or special issues, and the in England in 1882. It was the most pres- a few publishers are bringing out special pamphlets to tigious award at that time. In later years, the contribution mark the occasion. Even a few newspapers and magazines of Mendeleev received more attention. He had predicted have printed relevant articles. Since radiochemistry has a few missing elements, many of which, but not all, were contributed substantially to the extension of the Periodic found later to be correct. Table as well as to the development of various applica- The Periodic Table of Elements was originally con- tions related to it, this special issue of Radiochimica Acta structed empirically to take account of the periodicity is being published as a part of international celebrations. in their chemical properties. Some of the discoveries In this Editorial we shortly describe the origin and devel- starting in 1890s related to the structure and divisibility opment of the Periodic Table and give a brief overview of or even breakup of the (e. g. , radioactiv- its present status, discussing some related areas of par- ity, etc.) were not accepted by Mendeleev till his death ticular significance to radiochemistry. in 1907. He saw in them a threat to his own discovery of elements as individual units. Ironically, through subse- quent development of the and, above all, 2 Origin and development of the the , combined with the experimen- Periodic Table tal evidence that the and not the is the deciding factor in the characterisation of an A large number of chemical elements were discovered in element, the Periodic Table was embedded in a theoreti- the second half of the 18th century and the first half of the cal framework. 768 S. M. Qaim et al., Editorial: 150 years of the Periodic Table of Chemical Elements

3 Present status and areas of process) has been harnessed to produce electricity. It is a mature technology having been in use for more than interest 60 years. Worldwide about 450 reactors are in operation and 16 % of the total electricity production is of The present status of the Periodic Table of Elements and nuclear origin; in some countries, especially in France, it is some important related areas of interest are presented in more than 75 %. It is a very clean form of energy because in this special issue in a coherent way. It is divided into three its generation almost no CO is emitted. The major problem, parts, namely, and transactinides, nuclear energy, 2 however, is the formation of long-lived ­. and medical . In each area comprehensive Most of the present development efforts are therefore reviews written by authors in the forefronts of their respec- related to management and disposal of the waste. Exten- tive fields are presented. As Editors we greatly appreciate sive fundamental studies on speciation, immobilisation, their efforts. A brief overview of each area is given below. partitioning and transmutation of the waste, consisting of mainly actinides and long-lived fission products, are underway. Here the character of the Periodic Table 3.1 Actinides and transactinides of Elements plays an important role. The actinides and lan- thanides behave quite differently as compared to fission The Mendeleev’s Periodic Table of Elements ended with products which are mostly transition . (Z = 92). From 1940 onwards, Glenn T. Seaborg In Part B of this special issue some newer ideas in fuel and his co-workers at the University of California, Berke- reprocessing and partitioning of radioactive products, ley, USA, synthesised through nuclear reactions the ele- under development in China, India and the European ments (Z = 93) to (Z = 103) and, Union, are described in detail. The chemistry of some similar to the , a new series of elements, special elements, like , which pose ­difficulty the actinides, was established. It was based on a strong in fuel reprocessing, is elucidated. Furthermore, an ­collaboration between chemists and physicists over a ­analysis of the hitherto somewhat unknown effect of the of about 20 years. Efforts to make new elements actinides on is described for the first time. Finally, beyond lawrencium,­ i. e. transactinides, then slowed a timely report on the contamination of the Fukushima down. But a new pick-up came in the mid 1990s at the Nuclear Power Plant Station with actinides is presented. Heavy Research Facility in Darmstadt, Germany, with Today, the heavy mass region of the Periodic Table many national and international collaborations, followed of Elements is closely connected with the energy produc- by other intensified efforts at the Joint Institute of Nuclear tion via fission. Furthermore, some of the actinides are Research in , Russia, and later at the RIKEN labo- also used as energy sources in space research. It should, ratory in Japan. The Periodic Table of Elements is now however, be pointed out that the light mass region of the extended up to (Z = 118) where the seventh Periodic Table of Elements is also of great potential inter- period of the Periodic Table finishes. est for energy production via the fusion process. With the In Part A of this special issue the extension of the increasing progress in the international test reactor facil- Periodic Table beyond uranium is discussed in detail. ity (ITER) at Cadarache, France, the role of the chemistry The physico-chemical experiments leading to the discov- of light elements will certainly enhance. eries of various new elements are briefly described and the chemical properties deduced from very challenging studies on a few of each element produced are elu- 3.3 Medical radionuclides cidated, particularly with regard to their placement in the extended Periodic Table. A review of theoretical attempts Besides the extension of the Periodic Table beyond the to understand the very strong relativistic effects in the heavy element uranium, two lower mass elements not heaviest elements, which might destroy the periodicity of existent in were also artificially synthesised. They the chemical behaviour, is also presented. were named as (Z = 43) and (Z = 61). The former is a transition and the latter belongs to the group of rare . Because of its suitable 3.2 Nuclear energy nuclear properties and versatile chemistry a ­ 99m of technetium, namely Tc (T½ = 6.0 h) has become The tremendous amount of energy released in the splitting the most important radionuclide in diagnostic nuclear of the nucleus 235U when hit by a (i. e. the fission medicine involving Single Emission Computed S. M. Qaim et al., Editorial: 150 years of the Periodic Table of Chemical Elements 769

Tomography (SPECT). About 40 million patients per year Some of the above mentioned aspects of medical are investigated worldwide using this radionuclide. radionuclide development and application are treated in Some characteristics of the Periodic Table of Elements detail in Part C of this special issue. influence the various medical uses of radionuclides. The property of α-particle emission from many heavy mass nuclei makes them attractive for α-targeted therapy. In the 4 Conclusion region of the lightest mass elements, on the other hand, the radionuclides decay predominantly by emission. Over the last 150 years the Periodic Table of Elements has Since those elements are major constitutes of all living been extended to about double of its original size (in this systems, organ function studies can be advantageously period of time, 7 new natural radioelements and 28 arti- performed using Tomography (PET). As ficial radioelements were discovered), and the Periodic regards medium mass elements, a mixture of three decay Table has received a very strong scientific , thanks modes, viz. β− emission, β+ emission and capture to sophisticated physical and mathematical approaches (EC), occurs and the radionuclides are finding versatile attached to it. Its scope and applications have been exten- applications both in diagnosis and internal radiotherapy. sively broadened, starting from fundamental aspects Since most of those elements have metallic character, of relativistic influence on chemical bonding, covering the significance of organo-metallic complexes is rapidly fission and fusion energy systems and extending to organ enhancing. function studies via molecular imaging as well as to inter- The periodicity of the Periodic Table of Elements is nal radionuclide targeted therapy. Many more applica- reflected to some extent in the uptake of radionuclides tions are expected to emerge in the future. and by living systems. Alkali and alkali-like metal radionuclides (e. g. 38K, 82Rb, 201Tl1+) find application in cardiac flow studies. Other exam- Syed M. Qaim: Editor-in-Chief, Forschungszentrum Jülich, Jülich, Germany, E-mail: [email protected] ples are the specific attachment of radionuclides of triva- Jens-Volker Kratz: Co-Editor, Universität Mainz, Mainz, Germany, 86 177g lent metals (e. g. Y, Lu) to tumour seeking agents, or E-mail: [email protected] to biomolecules (via an analogue approach) for Eric Simoni: Co-Editor, Université Paris-Sud, Orsay, France, study of metabolic processes. E-mail: [email protected]