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Atomic Structure Timeline, He discovered that protons have an equal and…
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He discovered that protons have an equal and opposite charge as an electron.He used cathodes rays and at the same time discovered canal rays.He also determined that the mass of he proton is 1,840 times heavier than an electron.
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The discovery of radioactivity in uranium by French physicist Henri Becquerel in 1896 forced scientists to radically change their ideas about atomic structure. Radioactivity demonstrated that the atom was neither indivisible nor immutable.
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In 1909 Millikan began a series of experiments to determine the electric charge carried by a single electron. He began by measuring the course of charged water droplets in an electric field. He found that all of the drops had charges that were simple multiples of a single number, the fundamental charge of the electron.
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He discovered that all radioactive preparations were not unique elements, but rather that some of them were variants of known elements. In other words, atoms could have the same chemical properties but have different properties when it came to radioactivity.
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In 1932, James Chadwick bombarded beryllium atoms with alpha particles. An unknown radiation was produced. Chadwick interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton. This particle became known as the neutron.
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He contributed to atomic theory through formulating quantum mechanics in terms of matrices and in discovering the uncertainty principle, which states that a particle's position and momentum cannot both be known exactly.
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Through a series of experiments he found that the total mass of products and reactants in a chemical reactions is always the same. This led to the theory of the law of conservation of mass.
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