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465 BCE
Democritus' Hypothesis
Democritus hypothesized that atoms are invisible, differ in size, can not be created nor destroyed, they are constantly moving, and that there are an infinite number of them. -
Period: 464 BCE to
Democritus, Dalton, Thompson, Rutherford, and Bohr
These five scientist's discoveries and theories. -
John Dalton's Theory
Dalton's theory contains the statements that all matter is made of atoms, all atoms of a given element are identical, all compounds are two or more atoms, and a chemical reaction is the rearrangement of atoms. -
Thomson's Discovery
Thomson experimented with a cathode ray tube. He found that cathode Rays were negatively charged. He also found neon gas had positively charged particles. He then discovered electrons. -
Thomson's Model
Thomson used plum pudding to create his model. It was stated that an atom was made up of electrons that bounced around inside the atom. This was before the discovery of the nucleus. -
Rutherford's Model
Rutherford discovered the atomic nucleus led to his model of the atom. He placed the nucleus in the center and electrons revolved around the nucleus like a solar system. -
Bohr's Model
Bohr's model is a solar system like model that has an equal number of positive charge in the nucleus and the negative charge in the electrons that circle the nucleus.