BRAINCAKEDiscovery of Atomic Structure
1897: J. J. Thomson discovered the electron
Applying large voltages to gases at low pressure in a glass tube caused the gas to glow as it was struck by 'cathode rays' from the negative electrode which were electrons emitted from the cathode.
J. J. Thomson thought that the atom was a cloud of positive charge with tiny little negative electrons embedded in the cloud rather like the bits of fruit in a plum pudding.
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Key terms in this lesson
- alpha particle
- A helium nucleus, made of 2 protons and 2 neutrons, with a 2+ charge, emitted by some radioactive nuclei.
More in Atomic Structure
- Structure of the Atom
- Atomic Number and Mass Number
- Isotopes
- Relative Isotopic Mass
- Relative Atomic Mass
- Mass Spectrometer
- Relative Atomic Mass from a Mass Spectrometer
- Relative Molecular Mass from a Mass Spectrometer
All 19 lessons in Atomic Structure · All Edexcel AS-level Chemistry topics