Atomic Structure

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Dalton proposed that the atom is the smallest indivisible constituent of matter. His theory explained the law of conservation of mass, the law of constant composition, and the law of multiple proporti…

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Dalton’s theory failed partially because atoms were later found to contain smaller particles. The discovery of the electron showed that atoms are divisible and not the smallest indivisible units of ma…

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A cathode ray tube is a partially evacuated glass tube with two metal electrodes connected to a high-voltage source. The negatively charged electrode is the cathode and the positively charged electrod…

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In 1897, Thomson used a cathode ray tube and an electric field to show that cathode rays are streams of negatively charged particles. He also found that the e/m ratio was the same for different gases …

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Cathode rays are made of electrons, and electrons are the same in all atoms. Because of this, the nature of cathode rays does not depend on the gas in the tube or the metal used for the electrodes.

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An electron has a relative charge of -1 and a mass of 9.109389×10^-31 kg. It is much lighter than a proton.

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Goldstein used a perforated cathode in a discharge tube and observed a faint red glow behind the cathode. This showed the presence of anode rays, also called canal rays, which travel opposite to catho…

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Canal rays are formed when electrons remove one or more electrons from the gas atoms in the tube. Since different gases have different atoms and different numbers of protons, the positive ions formed …