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400
First Thoery
Democritus is the first person to theorize that everything is made up of atoms. -
400
Aristotle's Theory
He believed the elements were water, fire, earth, and air -
400
Democritus' Theory
Democritus discovers his atomic theory about atoms around 400 B.C.E. His theory states that everything around us is made up of atoms. He also stated that atoms are indivisble and cannot be broken down. -
John Dalton
Every element is made up of particles called atoms. All atoms of same element, atoms look same. Can't create or destroy them. Compounds are formed when atmos of different elements compine with one another -
J.J. Thompson's Plum Pudding Model
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J.J. Thompson's Discovery
J.J. Thomson discovered that all atoms have electrons outside the nucleus. He discovered this by doing a series of experiements desgined to study the nature of electric discharge in a high-vacuum cathode-ray tube. Thomson electrically charged plates and magnets as evidence of "bodies smaller than regular atoms." This experiment helped him discover electrons and how they are in every single atom. -
James Chadwick
In 1932 Chadwick discovered the particle in the nucleus of an atom that became known as the neutron because it has no electric charge. -
Rutherford's Experiment
He shot radiation at a gold sheet. His prediction was that the beam would go through the gold sheet. He was wrong and it reflected off. Concluded that the beam had positive charge and for it to bounce off the sheet, the sheet had to have a positive charge. Concluded that atoms have a nucleus
