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400 BCE
Democritus
He proposed that all matter, including space and time, was made up of small units called atoms. He had no experiments and had little evidence, but hi sides were kept on by Lucretius. -
John Dalton
Agreed that all matter was created by atoms, which he believed were indestructible. He also stated that compounds are created by combining two atoms, and that all atoms of given elements are identical in their mass and properties. -
Ernest Rutherford
Used the gold foil experiment to discover the modern model of an atom. He concluded that all positive charges were centralized, while negative electrons orbited the nucleus. -
JJ Thomson
Discovered the electron. He experimented by testing and studying the nature of electric discharge in a high vacuum cathode-ray tube. -
Niels Bohr
Explained that outer orbits in an atom could hold more electrons than inner orbits. By knowing this, one can determine the atom's chemical properties. He also gave birth to the idea that electrons emit light by jumping orbits.
