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460 BCE
Democritus
He proposed that all matter, including space and time, was made up of small units called atoms. He did no experiments and had little evidence, but his idea was kept on by Lucretius. -
John Dalton
Agreed that all matter was created by atoms, which he believed was indestructible. He also seeked that compounds are created by combining two atoms, and that all atoms of given elements are identical in their mass and properties. -
J.J. Thomson
Discovered the electron. He experimented by testing and studying the nature of electric discharge in a high vacuum cathode-ray tube -
Ernest Rutherford
Used the good foil experiment to discover the modern model of an atom. He concluded that all positive charges were centralized, while negative electrons orbited the nucleus -
Neils Bohr
Explained that outer orbits in an atom could hold more electrons than the inner orbits. . hold more electrons than the inner orbits. By knowing this, one can determine an atom’s chemical properties. He also discovered the idea that electrons emit light by jumping orbits. -
Heisenberg
Thought of the uncertainty principle. This principle states that one can never know the exact location and energy of an electron. -
Chadwick
Discovered the neutron. The neutron helps balance out protons in the nucleus of an atom.