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400
Democritus
This greek philosopher first suggested that all substances of tiny indestructible particles called atoms. -
Period: 400 to
.
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Daltons
HIs theory composed of:
-All matter consisted of atoms
-Atoms can not be divided
-Atoms of the same element were alike
-Atoms combined into simple whole number ratios -
Thomson
He discovered that electrons had a negative charge -
Rutherford
He proposed that the atom consisted of mostly empty space with a dense nucleus conatining positively charged protons -
Bohr
He suggested that electrons orbited the nucleus at different energy levels -
Chadwick
He dicovered that the nucleus contained particles called neutrons as well as protons
