![]() In 1908, Ernest Rutherford, a former student of Thomson's, proved Thomson's raisin bread structure incorrect. Bohr’s model and the current model are described in Chapter 6. The Evolution of Atomic Theory, as Illustrated by Models of the Oxygen Atom. Schematic of cathode ray tube with deflection. ![]() These particles were later named electrons.Īfter Eugen Goldstein's 1886 discovery that atoms had positive charges, Thomson imagined that atoms looked like pieces of raisin bread, a structure in which clumps of small, negatively charged electrons (the "raisins") were scattered inside a smear of positive charges. Thomson (18561940) proved that atoms were not the most basic form of matter. Thomson theorized, and was later proven correct, that the stream was in fact made up of small particles, pieces of atoms that carried a negative charge. Thomson found that the mysterious glowing stream would bend toward a positively charged electric plate. For years scientists had known that if an electric current was passed through a vacuum tube, a stream of glowing material could be seen however, no one could explain why. Thomson's notion of the electron came from his work with a nineteenth century scientific curiosity: the cathode ray tube. Thomson's work suggested that the atom was not an "indivisible" particle as John Dalton had suggested but a jigsaw puzzle made of smaller pieces. Thomson’s cathode ray tube experiments provided the first evidence that atoms were composed of even smaller particles called electrons. Thomson dramatically changed the modern view of the atom with his discovery of the electron. What did JJ Thomson’s cathode ray tube experiment show quizlet In 1897, J.J. Pierre Curie carried a vial of radium in his coat pocket to demonstrate its greenish glow, a habit that caused him to become ill from radiation poisoning well before he was run over by a horse-drawn wagon and killed instantly in 1906.In 1897, J. Cathode rays were determined to be composed of negatively charged particles that were smaller than the smallest atom. Prior to the experiment, it was not known that atoms were composed of further particles. Starting with several tons of pitchblende, the Curies isolated two new radioactive elements after months of work: polonium, which was named for Marie’s native Poland, and radium, which was named for its intense radioactivity. Thomson's cathode ray tube experiment discovered the subatomic particle the electron. She found that one particular uranium ore, pitchblende, was substantially more radioactive than most, which suggested that it contained one or more highly radioactive impurities. Marie Curie coined the term radioactivity (from the Latin radius, meaning “ray”) to describe the emission of energy rays by matter. Becquerel’s work was greatly extended by Marie Curie (1867–1934) and her husband, Pierre (1854–1906) all three shared the Nobel Prize in Physics in 1903. The second line of investigation began in 1896, when the French physicist Henri Becquerel (1852–1908) discovered that certain minerals, such as uranium salts, emitted a new form of energy. ![]() With this information and Thomson’s mass-to-charge ratio, Millikan determined the mass of an electron: Subsequently, the American scientist Robert Millikan (1868–1953) carried out a series of experiments using electrically charged oil droplets, which allowed him to calculate the charge on a single electron. Another set of electrode plates deflect the ray, with the ray bending towards the positive plate. Image used with Permission (CC BY-SA-NC). As the cathode rays travel toward the right, they are deflected toward the positive electrode (+), demonstrating that they are negatively charged. \): Deflection of Cathode Rays by an Electric Field.
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