Structure of Atom

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Matter was composed of extremely small particles called atoms which were structureless, possessed fixed mass and were indivisible. Atoms of a given element were alike and differed from atoms of other …

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Cathode rays are streams of electrons. They travel in straight lines, produce fluorescence, and get deflected towards the positive electrode in an electric field, showing that they are negatively char…

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The charge-to-mass ratio was found to be 1.759 × 10^8 C/g in 1897. This was measured using cathode rays and showed that the same particle was present regardless of the gas used.

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An electron has charge = 1.6021 × 10^-19 C and mass = 9.108 × 10^-28 g. It is about 1/1837 of the mass of a hydrogen atom.

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Millikan used the oil drop method in 1909. The present accepted value of electronic charge is 4.8032 × 10^-10 e.s.u. or 1.6022 × 10^-19 C.

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Canal rays are positive rays produced when a perforated cathode is used in a discharge tube. They deflect towards the negative electrode in an electric field, so they contain positively charged partic…

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The particles in canal rays are positive ions formed from the gas inside the tube. Since different gases form different ions, the e/m value changes with the gas used.

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A proton is a subatomic particle with mass 1.672 × 10^-24 g and charge +1.6021 × 10^-19 C. It is actually an ionised hydrogen atom and can be represented as H+.