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Period: 5 BCE to
Democritus proposed the existence of atoms.
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Period: to
Dalton developed his theory of atoms and matter.
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Period: to
JJ Thomson discovered the electron.
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Period: to
Rutherford developed the planetary model of the atom.
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Period: to
Bohr developed a model of the atom.
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Period: to
The proton was discovered.
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Period: to
The neutron was discovered.