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Democritus (greece)
Stated that all matter is made up of atoms. He also said that atoms cannot be destroyed and they are invisible and so small that they cannot be divided any further -
John Dalton
Formed the atomic theory, which states that al matter is made of tiny, unbreakable particles called atoms that are all alike and have the same atomic weight -
J.J Thomson
Discovered the electron and developed the plum-pudding model of the atom. -
Ernest 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. -
Neils Bohr
stated that the electrons moved around the nucleus in successively large orbits. He also presented the Bohr atomic model which stated that atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states. -
Chadwick
discovered the neutrally-charged neutron.