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400 BCE
Democritus
Democritus was an ancient greek pre-socratic philosopher. He is mainly known for his formulation of an atomic theory of the universe. -
John Dalton
John Dalton was an english chemist, physicist and meteorologist. He introduced the atomic theory into chemistry. He made the discovery that atoms of one element are all alike but they differ from atoms of other elements. -
Cathode Ray Tube Experiment
This experiment was conducted by J.J. Thomson discovered subatomic particles, the electron. Prior to the experiment it was unknown that atoms were constructed by other particles. -
Thomson "Plum Pudding Model"
Plum pudding is an english desert similar to blueberry muffins. The idea behind the model is that electrons are surrounded by a volume of positive charge. So the comparison was made that the electrons (plums) are surrounded by a volume of positive charge (pudding). -
The gold foil experiment
Through this experiment led scientists to discover that every atom has a nucleus where all of its positive charge and most of its mass is concentrated. This was conducted by measuring how an alpha particle beam is scattered after passing through a thin metal foil. -
Ernest Rutherford
Ernest rutherford has done a lot of different things, but he is best known for his studies on radioactivity and the atom. He conducted the gold foil experiment which led him to discover that the atom is made up of mostly empty space, and a very dense nucleus. -
Niels Bohr
He adapted Rutherford's nuclear structure to Mac Planck's quantum theory and created the Bohr model which is the most used model of the atom. He won a nobel piece prize for his contributions to the understanding of the atomic structure as well as quantum theory. -
Electron Cloud Model
This model shows an area in which an electron is likely to be. The model itself consisted of a dense nucleus surrounded by a cloud of electrons at various levels in orbitals.