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300
aristotle
Around 300BC Aristotle alone didn’t believe that atoms were of different sizes and had regular geometric shapes which contradicted societies belief for his day. He believed all matter contained fire, air, earth, and water and emotions of the world contributed to good and bad. At the time this was all new so accepted with no contridiction -
430
democritus
Around 430BC Democritus took the theory from his mentor and made a very significant observation for his lifetime, he stated that atoms are the building blocks for all things and that atoms are tiny, indivisible, and differ only by shape and arrangement. He also stated that atoms cannot be destroyed and his theory was very unaccurate. -
john dalton
In 1803 after many years of researching atoms John Dalton published his Theory on atoms. He worked off of Lavoisiers work on the atom. It didnt anwser any questions but it did fill in some of democritus work. this was also accurate at the time but far from our model. -
marie & pierre curie
Marie & Pierre Curie discovered two new elements and did alot of research on radioactivity. there idear was thought up by them selfs. tested by experimenting with uranium. thought of not on pourpose but acculy by comparing 2 uranium ores. -
henri becquerel
Henri was experimenting with an ore containing uranium in his lab and found on accident that if he left it on a photographic plate without any light the ore still left an image (experiment). That happened because uranium is radioactive (also what marie and pierre curie found out) and that was the first time it was documented as such. -
J.J. Thomson
Thomson used a cathode ray tube to inferr that there are small particles inside of every atom. This inference proved dalton's theory to be wrong. Particles can be divided. Through this expirament thomson also inferred that atoms must be negatively charged.Thomson purposed the plum pudding model which allowed scientefic advances to occur. The plum pudding model has electorns being more accuarte and close to our model. -
Ernest Rutherford
Ernest Rutherford was know for his famous gold foil experiment. He shot alpha particles at gold foil, most of them went right through the foil but some were reflected meaning there was a small, dense, positive charged area he called it a nucleus of an atom. He did this alone but was the building block for future scientist. -
Robert Millikan
Robert millikan alone found that by using his oil drop experiment, you could measured the charge of an electron. -
Niels Bohr
Neils suggested that electrons travel around the nucleus in definite paths. These paths are always at a certain level away from the nucleus. He basickly took rutherfords atomic model and changed it a little bit. He used quantium experiments to test his model. -
james chadwick
James chadwick discoved that there was a neutron inside the neuclus. He like bohr worked alot off of rutherfords model. He performed tests on a new type of radiation to prove this theory. -
Quantum model
The current day model of an atom is based on a theory of quantum mechanics. Each electron is thought of as a cloud, of negative charge, instead of one tiny negative particle. An atom consists of electrons, neutrons, and protons. This is based off of all past theorys and is what we see a atom as today.
