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500
Democritus
In the 5th century BCE Democritus stated that all matter is made up of tiny particles called atoms. Democritus beleived that if you halfed something enough times you would eventually get something small enough that couldnt be split again, and he called that an atom. He described an atom as being indestructable. -
John Dalton (Billiard Ball Model)
In 1803 John Dalton stated that every atom is a solid sphere and that each element was composes of the same kind of atoms. John Daltons model is described as a the "Billiard Ball Model" because his diagram of the model included no protons, electrons, or neutrons. It only included one solid sphere atom. -
John Thompson (Plumb Pudding Model)
In 1897 John Thompson stated that the atom was a sphere of positively charged electricity with negative particles imbedded throughout. His model is known as the Plumb Pudding Model because the electrons imbedded in the positively charged sphere is like the plumbs imbedded in the pudding. -
Period: to
Atomic Discoveries
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Ernest Rutherford Model
In 1911 Ernest Rutherford conducted his gold foil experiment. In his experiment Rutherford shot positively charged alpha particles through a very thin sheet of gold foil and when these alpha particles started to deflect off the gold sheet Rutherford discoved that in every atom there is a positively charged nucleus. Rutherfords model states that the atom is mostly made up of empty space with a dense positively charged nucleus surrounded by negative electrons. -
Neils Bohr Model (Planetary Model)
The Bohr model states that electrons revolve around the nucleus, occupying circular orbits with distinct energy levels. The analogy for this model is planets rotating in fixed orbits around the sun, just like electons orbiting around its nucleus. For electrons to move up in an energy level it must gain energy. -
Electon Cloud Model
The cloud theory was created by Erwig Schrodinger and Werner Heisenburg. They stated that an atom consists of a dense nucleus composed of protons and neutrons surrounded by electrons that exist in differenet clouds and energy levels. -
Uncertaincy Principle
In 1927 they discovered that the velocity nor the location of an electron was impossible to find and they called it the uncertaincy principle. This is why the location of electrons are displayed as a cloud because the exact location of an electon cannot be determined.
