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Francium is a chemical element; it has symbol Fr and atomic number 87. It is extremely radioactive; its most stable isotope, francium-223, has a half-life of only 22 minutes. It is the second-most electropositive element, behind only caesium, and is the second rarest naturally occurring element. Francium's isotopes decay quickly into astatine, radium, and radon. The electronic structure of a francium atom is [Rn] 7s1; thus, the element is classed as an alkali metal.
Lise Meitner was a Jewish Austrian physicist who was one of those responsible for the discovery of the element protactinium and would jointly confirm that nuclear fission was a replicable process within physics. While working on radioactivity at the Kaiser Wilhelm Institute of Chemistry in Berlin, she discovered the radioactive isotope protactinium-231 in 1917.
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
Otto Hahn was a German chemist who was a pioneer in the fields of radioactivity and radiochemistry. He is referred to as the father of nuclear chemistry and father of nuclear fission. Hahn and Lise Meitner discovered radioactive isotopes of radium, thorium, protactinium and uranium. He also discovered the phenomena of atomic recoil and nuclear isomerism, and pioneered rubidium–strontium dating. In 1938, Hahn, Meitner and Fritz Strassmann discovered nuclear fission, for which Hahn alone, was awarded the 1944 Nobel Prize for Chemistry. Nuclear fission was the basis for nuclear reactors and nuclear weapons.
Marguerite Catherine Perey was a French physicist and a student of Marie Curie. In 1939, Perey discovered the element francium by purifying samples of lanthanum that contained actinium. In 1962, she was the first woman to be elected to the French Académie des Sciences, an honor denied to her mentor Curie. Perey died of cancer in 1975.
The year 1941 in science and technology involved some significant events, listed below.
Otto Robert Frisch was an Austrian-born British physicist who worked on nuclear physics. With Otto Stern and Immanuel Estermann he first measured the magnetic moment of the proton. With Lise Meitner he advanced the first theoretical explanation of nuclear fission and first experimentally detected the fission by-products. Later, with his collaborator Rudolf Peierls he designed the first theoretical mechanism for the detonation of an atomic bomb in 1940.
John Ray Dunning was an American physicist who played key roles in the Manhattan Project that developed the first atomic bombs. He specialized in neutron physics, and did pioneering work in gaseous diffusion for isotope separation. He was dean of the school of engineering and applied science at Columbia University from 1950 to 1969.
Nazi Germany undertook several research programs relating to nuclear technology, including nuclear weapons and nuclear reactors, before and during World War II. These were variously called Uranverein or Uranprojekt. The first effort started in April 1939, just months after the discovery of nuclear fission in Berlin in December 1938, but ended only a few months later, shortly ahead of the September 1939 German invasion of Poland, for which many notable German physicists were drafted into the Wehrmacht. A second effort under the administrative purview of the Wehrmacht's Heereswaffenamt began on September 1, 1939, the day of the invasion of Poland. The program eventually expanded into three main efforts: Uranmaschine development, uranium and heavy water production, and uranium isotope separation. Eventually, the German military determined that nuclear fission would not contribute significantly to the war, and in January 1942 the Heereswaffenamt turned the program over to the Reich Research Council while continuing to fund the activity.
Friedrich Wilhelm Strassmann was a German chemist who, with Otto Hahn in December 1938, identified the element barium as a product of the bombardment of uranium with neutrons. Their observation was the key piece of evidence necessary to identify the previously unknown phenomenon of nuclear fission, as was subsequently recognized and published by Lise Meitner and Otto Frisch. In their second publication on nuclear fission in February 1939, Strassmann and Hahn predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction.
Ida Noddack, néeTacke, was a German chemist and physicist. In 1934 she was the first to mention the idea later named nuclear fission. With her husband Walter Noddack, and Otto Berg, she discovered element 75, rhenium. She was nominated three times for the Nobel Prize in Chemistry.
The Frisch–Peierls memorandum was the first technical exposition of a practical nuclear weapon. It was written by expatriate German-Jewish physicists Otto Frisch and Rudolf Peierls in March 1940 while they were both working for Mark Oliphant at the University of Birmingham in Britain during World War II.
Francis Goddard Slack was an American physicist. He was a physics teacher, researcher, and administrator in academia who was renowned for placing equal emphasis on teaching and on research.
Herbert Lawrence Anderson was an American nuclear physicist who was Professor of Physics at the University of Chicago.
G. Norris Glasoe was an American nuclear physicist. He was a member of the Columbia University team which was the first in the United States to verify the European discovery of the nuclear fission of uranium via neutron bombardment. During World War II, he worked at the MIT Radiation Laboratory. He was a physicist and administrator at the Brookhaven National Laboratory.
Eugene Theodore Booth, Jr. was an American nuclear physicist. He was a member of the historic Columbia University team which made the first demonstration of nuclear fission in the United States. During the Manhattan Project, he worked on gaseous diffusion for isotope separation. He was the director of the design, construction, and operation project for the 385-Mev synchrocyclotron at the Nevis Laboratories, the scientific director of the SCALANT Research Center, and dean of graduate studies at Stevens Institute of Technology. Booth was the scientific director of the SCALANT Research Center, in Italy.
Gottfried Freiherr von Droste (1908–1992), a.k.a. Gottfried Freiherr von Droste zu Vischering-Padberg, was a German physical chemist. He worked at the Kaiser Wilhelm Institute for Chemistry (KWIC). He independently predicted that nuclear fission would release a large amount of energy. During World War II, he participated in the German nuclear energy project, also known as the Uranverein. In the latter years of the war, he worked at the Reich's University of Strassburg. After the war, he worked at the Physikalisch-Technische Bundesanstalt (Federal Physical and Technical Institute and also held a position at the Technical University of Braunschweig.
The discovery of the neutron and its properties was central to the extraordinary developments in atomic physics in the first half of the 20th century. Early in the century, Ernest Rutherford developed a crude model of the atom, based on the gold foil experiment of Hans Geiger and Ernest Marsden. In this model, atoms had their mass and positive electric charge concentrated in a very small nucleus. By 1920, isotopes of chemical elements had been discovered, the atomic masses had been determined to be (approximately) integer multiples of the mass of the hydrogen atom, and the atomic number had been identified as the charge on the nucleus. Throughout the 1920s, the nucleus was viewed as composed of combinations of protons and electrons, the two elementary particles known at the time, but that model presented several experimental and theoretical contradictions.
Nuclear fission was discovered in December 1938 by chemists Otto Hahn and Fritz Strassmann and physicists Lise Meitner and Otto Robert Frisch. Fission is a nuclear reaction or radioactive decay process in which the nucleus of an atom splits into two or more smaller, lighter nuclei and often other particles. The fission process often produces gamma rays and releases a very large amount of energy, even by the energetic standards of radioactive decay. Scientists already knew about alpha decay and beta decay, but fission assumed great importance because the discovery that a nuclear chain reaction was possible led to the development of nuclear power and nuclear weapons. Hahn was awarded the 1944 Nobel Prize in Chemistry for the discovery of nuclear fission.
References
- ↑ Phys. Rev.55: pp. 374–381. 1939.
- ↑ Phys. Rev.56: pp. 455–459. 1939.
- ↑ "The Nobel Prize in Physiology or Medicine 1948". NobelPrize.org. Retrieved May 11, 2011.
- ↑ Snyder, John P. (1993). Flattening the Earth: Two Thousand Years of Map Projections. University of Chicago Press. ISBN 978-0-226-76747-5.
- ↑ van der Krogt, Peter. "87 Francium". Elementymology & Elements Multidict. Retrieved January 7, 2019.
- ↑ MacCorquodale, D. W.; Binkley, S. B.; Thayer, S. A.; Doisy, E. A. (1939). "On the Constitution of Vitamin K1". Journal of the American Chemical Society. 61 (7): 1928–1929. doi:10.1021/ja01876a510.
- ↑ "Linus Pauling: The Nobel Prize in Chemistry 1954". Nobel Lectures, Chemistry 1942–1962. Elsevier. 1964. Retrieved February 28, 2007.
- ↑ Smith, Michael (2007). Station X: the Codebreakers of Bletchley Park. Pan Grand Strategy Series (rev. ed.). London: Pan Macmillan. p. 60. ISBN 978-0-330-41929-1.
- ↑ Mollenhoff, Clark R. (1988). Atanasoff: Forgotten Father of the Computer . Ames: Iowa State University Press. ISBN 978-0-8138-0032-5.
- ↑ Shapin, Steven (1996). The Scientific Revolution. University of Chicago Press.
- ↑ Crilly, Tony (2007). 50 Mathematical Ideas you really need to know. London: Quercus. p. 133. ISBN 978-1-84724-008-8.
- ↑ Hahn, O.; Strassmann, F. (January 6, 1939). "Über den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle". Naturwissenschaften . 27 (1): 11–15. Bibcode:1939NW.....27...11H. doi:10.1007/BF01488241. S2CID 5920336.
- ↑ Meitner, Lise; Frisch, O. R. (February 16, 1939). "Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction". Nature . 143 (3615): 239–240. Bibcode:1939Natur.143..239M. doi:10.1038/143239a0. S2CID 4113262. Archived from the original on May 25, 2011. Retrieved 22 May 2011.
- ↑ Frisch, O. R. (February 18, 1939). "Physical Evidence for the Division of Heavy Nuclei under Neutron Bombardment". Nature. 143 (3616): 276. Bibcode:1939Natur.143..276F. doi: 10.1038/143276a0 .
- ↑ Announcement of the Atomic Age plaque next to the entrance of the Physics Department at GWU (erected 2002).
- ↑ Levine, P.; Stetson, R. E. (1939). "An unusual case of intragroup agglutination". JAMA . 113 (2): 126–7. doi:10.1001/jama.1939.72800270002007a.
- ↑ Clifton J., Philips (1971). "Fearn, Anne Walter". In James, Edward T. (ed.). Notable American Women, 1607-1950: A Biographical Dictionary. Vol. 1. p. 603. ISBN 978-0-67462-734-5.
- ↑ Tiehm, Arnold (1985). "Fanny Searls (1851-1939)". Brittonia. 37 (1): 42. doi:10.1007/BF02809668. S2CID 87755152.