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Democritus
He formulated an atomic theory which stated that everything was composed of atoms. Democritus and his mentor, said that atoms can't be destroyed and are different in shape and size. -
Issac Newton
He theorised a mechanical universe with small solid masses in motion and said that atoms in molecules are bind together by forces. -
John Dalton
Proposed an atomic theory which stated that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together. -
George Johnstone Stoney
Introduced the "fundamental unit quantity of electricity" which was electrons. His contribution became part of the discovery of electrons. -
Joseph John Thomson
He discovered electrons and proposed the plum pudding model of the atom. When he discovered electrons, he knew that they had a negative charge and thought that matter must have a positive charge. -
Max Planck
He founded the quantum theory which showed that when atoms vibrate strong enough, it can cause objects to light up which would then measure the energy. -
Hantaro Nagaoka
Propsoed an atomic model, "Saturnian Model". The atom model, which made two predictions, was an analogy to the explanation of the stability of Saturn rings. -
Robert Millikan
Found the measurement of the charge and mass of a single electron while working on an oil drop experiment. -
Ernest Rutherford
With the results of an experiment, he suggested that electrons orbited around a positive centre. -
Henry Gwyn Jeffreys Mosely
While studying the x-rays of various elements he saw that each element produced its own distinct set of wavelengths. He then showed that these x-ray wavelength could be better correlated with the atomic number which made him discover the number protons in an element determines its atomic number. -
Niels Bohr
In one of his experiment, he found that electrons can only orbit at a certain distance from the nucleus and an atom absorbs energy when an electron gets boosted from a low energy orbit to a high energy orbit. -
James Chadwick
Discovered neutron which led onto the possibility to create elements heavier than Uranium.
