Pierre and Marie Curie, Henri Becquerel and the discovery of radioactivity By: Jordan Lisse & Wyatt Amdor

Henri Becquerel ● Born - 15 December 1852 Paris, FranceFrance ● Died - 25 August 1908 (aged 55) Le Croisic, Brittany, FranceLe Croisic ● Completed work at École Polytechnique and the École des Ponts et Chaussées ● 1890 he married Louise Désirée Lorieux

● Becquerel's early work focused on the polarization of light phosphorescence and terrestrial magnetism. ● In 1896, he made his greatest discovery: radioactivity. ● Following a discussion with Henri Poincaré on the recent discovery of X-rays, Becquerel devised an experiment that proved the existence of this naturally occurring force. ● Although his initial experiments were not successful he came upon evidence of natural radioactivity nearly by accident, when an unexpected reaction occurred in one of his laboratory drawers. Significant Works

The Discovery of Radioactivity conducting an experiment which started with the exposure of a uranium-bearing crystal to sunlight. Once the crystal was exposed to sunlight for a while, he placed it on a photographic plate. As he had anticipated, the crystal produced its image on the plate. Becquerel theorized that the absorbed energy of the sun was being released by the uranium in the form of x-rays. Further testing of this theory had to be put off for a few days because the sky had clouded up and the sun had disappeared. For the next couple of days he left his sample of uranium in a closed drawer along with the photographic plate. When the weather had cleared, he returned to the drawer to retrieve his gear. He was surprised to find that the crystal had left a clear, strong image on the photographic plate. How could this be? There was no source of energy to produce the image! What Becquerel had discovered was that a piece of mineral which contained uranium could produce it's image on a photographic plate in the absence of light. What he had discovered was radioactivity! He attributed this phenomenon to spontaneous emission by the uranium.

Pierre Curie ● Born - 15 May 1859 in Paris, France ● Died - 19 April 1906 (aged 46) in Paris, France ● Completed work at the School of Physics and Industrial Chemistry at Paris

Important Works by Pierre Curie ● Before his famous studies on magnetism, he designed and perfected an extremely sensitive torsion balance for measuring magnetic coefficients. ● Pierre Curie studied ferromagnetism, paramagnetism, and diamagnetism for his doctoral thesis, and discovered the effect of temperature on paramagnetism which is now known as Curie's law ● Pierre made the first discovery of nuclear energy, by identifying the continuous emission of heat from radium particles.

Works continued ● He was able to show that some of the emissions were positively charged, some were negative and some were neutral. These correspond to alpha, beta and gamma radiation. ● Curie is a unit of radioactivity (3.7 × decays per second or 37 gigabecquerels) ● originally named in honor of Curie by the Radiology Congress in 1910, after his death

Marie Curie ● Born - 7 November 1867 Warsaw, Kingdom of PolandKingdom of Poland ● Died - 4 July 1934 (aged 66) Passy, Haute-Savoie, France ● Completed work at the School of Physics and Industrial Chemistry at Paris & French Academy of Medicine

Important works by Marie Curie ● Curie took Becquerel's work a few steps further, conducting her own experiments on uranium rays. ● She discovered that the rays remained constant, no matter the condition or form of the Uranium. ● This revolutionary idea created the field of atomic physics and Curie herself coined the word radioactivity to describe the phenomena. ● Working with the mineral pitchblende, the pair discovered a new radioactive element in Pitchbelnde- a form of the mineral uraninite occurring in brown or black pitch-like masses.

Works Continued ● They also detected the presence of another radioactive material in the pitchblende, and called that radium. ● In 1902, the Curies announced that they had produced a decigram of pure radium, demonstrating its existence as a unique chemical element. ● They named the element polonium, after Marie's native country of Poland.

● Her own work after 1906 tended more toward radiochemistry, and consisted, primarily, of investigations of the radioactive elements (including the substances that came to be called isotopes ) and their disintegration processes and products. ● the development of instrumentation for the detection of subatomic particles ● characterizations of the range (distance traveled from source) and energy of α-particle ● descriptions of the effects of α-particle on chemical processes Contribution to Atomic Theory

● investigation of β-rays ● the disintegration products in the thorium series. ● Marie Curie's Nobel Prize in chemistry (1911) was awarded for her discoveries of radium and polonium, and the isolation of radium and the study of its properties. Contributions Continued

Works Cited ● ● ● ● ●