Discoveries of new Elements

Although chemical theory was old fashioned during the early 18 century both laboratories and analytical chemistry were developing. Many governments were utilitarian and liked to find new sources for valuable minerals in the own country. These efforts resulted in the discovery of many new elements, as shown in Table 2.2. 

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But what would become of Mendeleev s periodic system which now seemed to consist of 300 or so "elements" To some chemists, the discovery of isotopes implied the end of the periodic system as it was known.3 These chemists suggested that it would be necessary to consider the individual new isotopes as the new "elements." But the chemist Paneth adopted a less reductionist approach, arguing that the periodic table of the familiar chemical elements should be retained because it dealt with the "elements" that were of interest to chemists. A justification for this view was provided by the fact that, with a few exceptions, the chemical properties of isotopes of the same element are indistinguishable.4 Moreover, Paneth appealed to Mendeleev s distinction between the two senses of the concept of an "element" in order to provide a philosophical rationale for the retention of the chemist s periodic table. Paneth argued that the discovery of isotopes of the elements represents the discovery of new elements as simple substances, whereas periodic... 

Before continuing the story of the discovery of the chemical elements, it will be necessary to outline the early attempts at classification made by Dobereiner, Begtiyer de Chancourtois, and Newlands, and to discuss briefly the periodic system of the elements which teas developed independently by Lothar Meijer and Mendeleev. This classification enabled Mendeleev to predict the properties of a number of undiscovered elements and of their compounds with surprising accuracy, and proved to be of great assistance in all subsequent discoveries of new elements. 

Winkler, C., The discovery of new elements within the last twenty-five... 

The discovery of uranium fission by Enrico Fermi and L. Szilard at Columbia University opened the way for further advances. This work was done under the cloak of wartime secrecy and led directly to the atomic bomb, but its significance for the discovery of new elements was very great. 

From ancient times, humans have pondered what the universe is made of Early philosophers proposed fire, earth, water, and air either individually or in combination as the building blocks of nature. Lavoisier defined an element operationally as a substance that cannot be broken down chemically. Using this definition, the number of elements has increased from around 30 in Lavoisier s time to over 115 today. The initial search for elements involved classical methods such as replacement reactions, electrochemical separation, and chemical analysis. New methods such as spectroscopy greatly advanced the discovery of new elements during the twentieth century. The last half century has been marked by the synthesis of elements by humans. 

Charles Hatchett reported in 1802 his discovery of columbium (niobium), and expressed a recurring view that the seemingly endless discovery of new elements would eventually cease. 

Harris was the first African American to work on the discovery of new elements. In a 1973 interview, he described how hard it could be for a black man to find work as a chemist. Employers would sometimes make him do simple adding and subtracting tests, because they did not believe he could do more complicated math and science problems. 

The Discovery of New Elements and the Boundary Between Physics and Chemistry in the 1920s and 1930s. The Case of Elements 43 and 75... 

The Discovery of New Elements and the Boundary Between Physics and Chemistry... 

This new kind of tool to find the missing elements was celebrated by Segre at the beginning of one of his papers. [46] He says that every time physics has provided chemistry with a new tool, it allowed the discovery of new elements, and he lists radioactivity, spectroscopy, and now the cyclotron. Nevertheless, the proof of the existence of and the actual detection of the isotopes of element 43 is first of all chemical, very much in the same way as Ida had criticized Fermi s conclusion in 1934. Segre even published the radioactive part in another journal [47]... 

I shall endeavor to show, as briefly as possible, in how far the periodic law contributes to enlarge our range of vision. Before the promulgation of this law the chemical elements were mere fragmentary, incidental facts in Nature there was no special reason to expect the discovery of new elements, and the new ones which were discovered from time to time appeared to be possessed of quite novel properties. The law of periodicity first enabled us to perceive undiscovered elements at a distance which formerly was inaccessible to chemical vision... 

The Periodic Table initiated the discovery of new elements which can be divided into three phases, overlapping chronologically ... 

Refinement in the measurements of atomic mass, the ordering of the elements based on atomic number rather than atomic mass by Henry G. Moseley (1887-1915) in 1913, and the discovery of new elements have led to the continuing evolution of the periodic table. But since Mendeleev s time the periodic table has remained basically unchanged, providing testament to the power of his original insight. 

Discoveries of a very large number of new elements have been claimed in recent times. Charles Baskerville, in the presidential address delivered before the chemists of the American Association for the Advancement of Science, St. Louis, 1903, gives a list5 of more than 180 such announcements since 1777. Of these only about 36 may be considered as actual discoveries of new elements, while over 130 have failed of confirmation or have been definitely rejected because the observations were made upon impure materials or upon elements already known. Of the remainder some may still be considered as having an undetermined status and others are what we now call isotopes. 

From 1961 to 1971, Seaborg served as the chairman of the US Atomic Energy Commission (now the Department of Energy). In this position he had an important role in establishing international treaties to limit the testing of nuclear weapons. Upon his return to Berkeley, he was part of the team that in 1974 first identified element number 106. In 1994, to honor Seaborg s many contributions to the discovery of new elements, the American Chemical Society proposed that element number 106 be named seaborgium (Sg). After several years of controversy about whether an element should be named... 

The concept of atomic number clarified some problems in the periodic table of Moseley s day, which was based on atomic weights. For example, the atomic weight of Ar (atomic number 18) is greater than that of K (atomic number 19), yet the chemical and physical properties of Ar are much more hke those of Ne and Kr than like those of Na and Rb. When the elements are arranged in order of increasing atomic number, Ar and K appear in their correct places in the table. Moseley s studies also made it possible to identify holes in the periodic table, which led to the discovery of new elements. 

This lull in the history of discoveries of new elements was ended by the spectral method developed in 1859-1860 by the German scientists R. Bunsen and G. Kirchhoff. And at once reports appeared about the discovery of new elements, which announced themselves via new spectral lines. Four chemical elements (cesium, rubidium, thallium, and indium) came to light owing to the spectroscopic method. 

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