![]() She had also discovered both Polonium and Radium, naming them after Poland and the word Ray respectively. 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. Marie’s biggest contribution to the atomic theory was that atoms’ arrangement did not lead to them being radioactive, but that the atoms themselves were radioactive instead. 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. 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 now put the Curie electrometer to use in measuring the faint currents that can pass through air that has been bombarded with uranium rays. ![]() About 15 years earlier, Pierre and his older brother, Jacques, had invented a new kind of electrometer, a device for measuring extremely low electrical currents. Marie Curie coined the term radioactivity (from the Latin radius, meaning “ray”) to describe the emission of energy rays by matter. A clever technique was her key to success. 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. Schematic of cathode ray tube with deflection. 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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