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Challenging the Structure and Properties of Atoms
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- 19th Century Scientific Journey: At the end of the 19th century the major challenge was to reveal the structure and the properties of the atom.
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Indivisibility of Atoms through the Conduction of Electricity
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- One of the first indications that atoms are not indivisible, comes from studying static electricity and the condition under which electricity is conducted by different substances.
- Many scientists contributed in revealing the presence of charged particles in an atom.
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J.J. Thomson
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- Electron and Challenging the Notion of Indivisible Atoms: In 1900, J.J. Thomson identified that the atom was an indivisible particle but contained at least one subatomic particle – the electron (represented as ‘e– ’).
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E. Goldstein’s 19th Century Revelation in Subatomic Exploration
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- Even before the electron was identified, E. Goldstein in 1886 discovered the presence of new radiations in a gas discharge and called them canal rays.
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Discovery of Proton
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- Canal Rays Connection: Canal rays were positively charged radiations which ultimately led to the discovery of another subatomic particle named proton (represented as p+) which had a charge, equal in magnitude but opposite in sign to that of the electron.
- Its mass was approximately 2000 times that of the electron.
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Particle Charges and Mass Disparities
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- The mass of a proton is taken as one unit and its charge as plus one whereas the mass of an electron is considered to be negligible and its charge is minus one.
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Neutrality in Atoms
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- It seemed that an atom was composed of protons and electrons, mutually balancing their charges.
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