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400
Democritus
Democritus was a Greek Philosopher that proposed that small particles called atoms make up all matter. He is a very important figure in the science world today, without him, we wouldn't know what an atom is. Around 400 B.C. -
John Dalton
A British scienctist and school teacher reintroduces the concept of atoms with evidence to support his ideas. He was the savior of the "atom" theory. -
J.J. Thompson
Identified electrons as particles that are present in every form of atom. -
Ernest Rutherford
A physicist from New Zealand discovers the positively charged nucleus of the atom. He played an important contribution to the theory by finding more information about what atoms look like. -
Niels Bohr
Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities.