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Leucippus and his pupil, Democritus, came up with the idea that matter is made up of tiny particles.
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Antoine Lavoisier proposed a law that says even if the matter changes its shape or form, its mass stays the same.
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John Dalton discovered that elements exist as discrete packets of matter.
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In the 1870s, scientists began to use discharge tubes to probe what stuff was made of.
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Eugen Goldstien found that cathode ray tubes also emitted light from the positive electrode.
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J. J. Thompson made the discovery that cathode rays are actually very small, very light particles, which he called corpuscles. We call them electrons.
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Ernest Rutherford conducted an experiment the he concluded that the entire positive charge in an atom must be concentrated in a very small area. He called this area the nucleus.
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Ernest Rutherford discovered that if he bonded nitrogen and alpha particles, he could create hydrogen ions. He said that these ions were fundamental particles. Protons.
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Niels Henrik David Bohr created a model of an atom that can be applied to any element.
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Verner Heisenberg found that it is impossible to know with certainty the momentum of an electron or particle. He proposed that the number of electrons in an atom aren't particles or waves. The had properties of both. He came up with the hypothesis that there are regions in an atom where electrons are much more likely to be. These regions are called orbitals.
