John Dalton 1803 - Atomic Theory
- Matter is made up of indivisible atoms.
- All atoms of an element are identical.
- Atoms are neither created nor destroyed.
- Atoms of different elements have different weights and chemical properties.
- Atoms of different elements combine in simple whole numbers to form compounds.
Michael Faraday 1830
- Set up a pair of metal plates sealed in a glass tube. The tube was filled with a gas, and the metal plates were connected to a series of batteries.
- As the pressure of the gas decreased, the gas began to glow.
- Julius Plucker (1858) noticed that only one end emitted light.He also changed the position of the patch of glass that glowed by bringing
a magnet close to the tube. - Conclusion: The effect of the magnetic field as evidence that whatever
produced this glow was electrically charged. - Cathode - metal plate connected to the negative end
- Anode - metal plate connected to the positive end
Johannes Hittorf 1869
- Found that when a solid object was placed between the cathode and anode, a shadow was cast on the end of the tube across from the cathode.
- Conclusion: Some beam or ray is given off by the cathode - subsequently called the tubes cathode-ray tubes.
William Crookes 1879 - Developed a better vacuum pump that allowed him to produce cathode-ray
tubes with a smaller residual gas pressure. - Conclusion: Cathode r0ays are negatively charged by studying deflection
of cathode rays by magnetic fields.
J.J. Thompson 1897
- Found that cathode rays could be deflected by an electric field
- Showed that cathode "rays" were actually particles
- Found the charge to mass ratio of the particles to be approximately
108 Coulomb (C) per gram. - Same charge to mass ratio regardless of metal used for cathode/anode
or gas used to fill the tube. - Conclusion: Particles were a universal component of matter.
- Electron - (originally called corpuscles by Thompson) particles
given off by the cathode; fundamental unit of negative electricity
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