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400
Democritus
In 400BC Democritus stated that all matter is made up of atoms. He also said that atoms are invisible, so small they can’t be divided, and that they fill up the space they’re in. -
Lavoisier
In 1777, Lavoisier came up with the formula for the conservation of matter in chemical reactions, and also told the difference between an element and a compound. -
John Dalton
In 1803, Dalton formed the atomic theory, which states that all matter is composed of tiny, indestructible particles called atoms that are all alike and have the same atomic weight. -
J.J Thomson
In 1898, Thomson discovered the electron and developed the plum-pudding model of the atom. -
Rober Milikan
In 1908, Milikan found out the electric charge of the electron. -
Ernest Rutherford
In 1909 Rutherford used the results of his gold-foil experiment to state that all the mass of an atom were in a small positively-charged ball at the center of the atom. -
The Gold-Foil Experiment
Rutherford conducted the gold-foil experiment that involved the firing of radioactive particles through thin metal foils and detecting them using screens coated with zinc sulfide. Rutherford found that although most of the particles passed straight through the foil approximately 1 in 8000 were deflected leading him to his theory that most of the atom was made up of 'empty space'. -
Neils Bohr
In 1913 Bohr stated that the electrons moved around the nucleus in large orbits. He also presented the Bohr atomic model which stated that atoms absorb radiation only when the electrons abruptly jump between allowed, or stationary, states.
