DISCOVERY OF THE ELEMENTS

The isotope produced was the 20-hour 255Fm. During 1953 and early 1954, while discovery of elements 99 and 100 was withheld from publication for security reasons, a group from the Nobel Institute of Physics in Stockholm bombarded 238U with 160 ions, and isolated a 30-min alpha-emitter, which they ascribed to 250-100, without claiming discovery of the element. This isotope has since been identified positively, and the 30-min half-life confirmed. 

Manufacture and Processing. The industry related to iodine production began a few years after the discovery of the element by Courtois in 1811. The production processes are based on the raw materials containing iodine seaweeds, mineral deposits, and oh-weh or natural gas brines. 

Marie Curie (Paris) discovery of the elements radium and polonium, the isolation of radium, and the study of the nature and compounds of this remarkable element. 

Fig. 2-9. The discovery of the elements. A. The total number of elements known as a function of lime. B. The number of elements discovered in each half-century since 1700.

Astronomers use spectroscopy to identify the composition of the sun and other stars. A striking example is the discovery of the element helium. In 1868, astrono-mers viewing a solar eclipse observed emission lines that did not match any known element. The English astronomer Joseph Lockyer attributed these lines to a new element that he named helium, from hellos, the Greek word for the sun. For 25 years the only evidence for the existence of helium was these solar spectral lines. 

Morris, Richard. The last sorcerers the path from alchemy to the periodic table. Washington (DC) Joseph Henry P, 2003. xii, 282 p. ISBN 0-309-08905-0 Contents Preface — 1. The four elements — 2. Prelude to the birth of chemistry — 3. The sceptical chymist — 4. The discovery of the elements — 5. A nail for the coffin — 6. "Only an instant to cut off that head" — 7. The atom — 8. Problems with atoms — 9. The periodic law — 10. Deciphering the atom — Epilogue the continuing search — appendix. A catalog of the elements — Further reading — Index... 

The chronology of the discovery of the elements is a textbook example of scientific development Three phenomena are particularly clear. 

Marshall, James Discovery of the Elements. Pearson Custom Publishing (1998)... 

The discovery of the elements 43 and 75 was reported by Noddack et al. in 1925, just seventy years ago. Although the presence of the element 75, rhenium, was confirmed later, the element 43, masurium, as they named it, could not be extracted from naturally occurring minerals. However, in the cyclotron-irradiated molybdenum deflector, Perrier and Segre found radioactivity ascribed to the element 43. This discovery in 1937 was established firmly on the basis of its chemical properties which were expected from the position between manganese and rhenium in the periodic table. However, ten years later in 1937, the new element was named technetium as the first artificially made element. 

The Development of Modern Chemistry. Harper and Row, New York, 1964, xii + 851 pp. including illustrations, Appendixes, (Discovery of the Elements, Discovery of Natural Radioactive Isotopes, Radioactive Decay Series, Nobel Prize Winners in Chemistry, Physics, and Medicine), and Bibliographic Notes. 

Francium - the atomic number is 87 and the chemical symbol is Fr. The name derives from the country France , where the French physicist Marguerite Percy from the Curie Institute in Paris, France discovered it in 1939 in the alpha particle decay of actinium, Ac => He => Fr, which was known as actinium-K and has a half-life of 22 minutes. An earlier claim of discovery in 1930 with the element name Virginium was determined to be incorrect. A similar claim for discovery of the element with atomic number 87 and named moldavium was also determined to be incorrect. The longest half-life associated with this unstable element is 22 minute Fr. 

Sometime later in 1869, vanadium metal was isolated from its ores by Henry Enfield Roscoe (1833—1915), but Sefstrom had already received credit for the discovery of the element vanadium. 

The E-pH diagram for 10 M Ra is presented in Figure 6.6. This concentration is used because such a solution of the most long-lived radium isotope Ra-226 (half-life 1620 years) would be decaying at the rate of about 3 billion atoms per minute per liter. Such a radioactivity could be worked with given special apparatus and precautions, but more concentrated solutions would require more demanding measures. The discovery of the element Ra was in 1898 by Marie Sklodowska Curie, Pierre Curie, and M. G. Bemont who isolated its salts from large quantities of pitchblende. 

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