Atomic theory timeline
Storyboard Text
- Democritus was a Greek philosopher who lived around 400 BC and believed that atoms were small, hard partials that were unable to break. He called these partials 'atomos' but we soon renamed them atoms
- The smallest piece of matter is indivisible...
- Aristotle was another Greek philosopher in 300 BC to the early 1800's who believed that matter was only made of 4 elements: Fire, Earth, Water, and Air. He had a tight grip on the audience at the time , so they believed his theories for centuries.
- Matter only has 4 properties: hot, cold, dry, and wet!
- John Dalton was a chemist in the early 1800's. He believed that all matter is made of atoms that are too small to see. He also believed that they were uncut able and indestructible.
- All atoms of a given element are exactly alike. Atoms of different elements are different.
- In 1897 J.J. Thomson, an English scientist, discovered the presents of negative particles in an atom. He made a model of his discovery and some people called it the "plum pudding" model because of how it looked.
- Atoms are made from a positive charge substance with negatively charged electrons scattered about .
- In 1908 Ernest Rutherford proved that atoms are not a "plum pudding" filled with positive materials. He theorized that atoms have a small positively charged center called the nucleus. The negative particles orbited around the nucleus at a distance.
- The nucleus is smaller than the atom. An atom is mostly empty space!
- In 1913 Niels Bohr improved the atomic model. He concluded that the mass of an atom is in the nucleus and also believed that the electrons move around the nucleus like how the planets orbit the sun.
- The way the electrons orbit the nucleus, is much like how the planets orbit the sun!
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