Atomic Theory Timeline
Storyboard Text
- Democritus was the first person to begin the search for a description of matter. He named the smallest piece of matter "atoms," which is a greek meaning of "not to be cut."
- 400 B.C.
- I am very old!
- Aristotle was a trusted philosopher in ancient Greece who stated matter is made of only four elements: fire, air, water, and earth. He also believed that matter only had four properties: hot, cold, dry, and wet.
- 300 B.C.
- Dalton was an English chemist that performed many experiments which led to the acceptance of atoms. He theorized that all matter is made of atoms, as well as the idea of an element having alike atoms.
- 1803
- An English scientist named J.J. Thomson hinted towards something even smaller than an atom; these being positive and negative particles. (electrons) He also proposed the "Plum Pudding" model.
- 1897
- Rutherford, a New Zealand-born physicist, performed an experiment using positively-charged particles fired at gold foil. Through this experiment, he proved atoms are not a "pudding" and had a nucleus.
- 1908
- The Danish scientist named Niels Bohr proposed an improvement to the atomic model. He theorized that the mass of an atom was mostly contained in the nucleus, as well as electrons move in definite orbits around the nucleus.
- 1913
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