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Democritus developed the intial idea of an atom. He believed that matter was made up of small invisible particles called atoms.
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Aristotle thought that Democritus was wrong about his atomic theory that the world was composed of small particles. He believed that the world was made up of air, water, fire and earth.
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Dalton did multiple experiments to prove that matter consisted of small particles called atoms. This lead to Dalton's Atomic theory. His model shows the fixed relations that connect atoms, but it does not show the forces which hold the atoms together in compounds. This theory was later discarded after JJ Thomson discovered the electron.
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Michael Faradsay discovered that matter has an electrical nature that consists of fixed quantities of electricity.
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Mendeleev created the first version of the periodic table.
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He proposed the theory of electromagnetism which also made a connection between light and electromagnetic waves in atoms.
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Stoney proposed that electricity was made up of nagative particles. He prposed the name electrons for the unit of electrical charge.
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Goldstein helped contribute to the discovery of the proton.
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Becquerel discovered that there are spontaneous emissions of radiation from the nucleus . There are three types of radiation being emitted- positive, negative and neutral.
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Thomson discovered the electrons in atoms. He produced the 'raisin cake' model which showed that the electrons all have the same mass and charge. He proved Democritus' theory wrong- atoms are not invisible but ratehr made up of small components.
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Nagaoka thought that Thomson's model of the atom was incorrect so he created his own model. His model resembled Saturn with its rings of electrons surrounding the sphere centre. This model was later proven to be inaccurate.
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Millikan experimented using oil to determine the charge of an electron.
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Rutherford created the first model of the atom that had a nucleus. He discovered that the atom has a poistively charged nucleus which is small but has a large mass. In his model, negatively charged particles surround the atom.
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Bohr proposed an explanation for the fact that atoms with moving particles do not collapse . He discovered that electrons with the same energy move in the same energy level.
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Soddy came up with the concept of isotopes. He discovered that some elements have different forms with different atomic weights.
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Louis De Brogile discovered that small, moving particles have a wave nature. Each moving partticle has both particle and wave properties just like light. This was confirmed by Davisson and GP Thompson.
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Erwin Schrodinger created a wave mechanical model where moving electrons formed a three dimensional wave that surrounds the nucleus.
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Heisenberg thought that it was impossible to know the position and velocity of an electron at the same time.
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Max Born edited Schrodingers quantum mechanics equation. This helped scientists develop the model of the atom with a nucleus surrounded by electrons at different locations when they are in different energy states.
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Chaswick discovered the neutral particles in the nucleus. He called them neutrons.
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Murray Gell-Mann discovered that all the components of an atom are held together by quarks. Both proposed the idea of quarks and then proceded to test for electrical charges in atoms.
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https://atomictimeline.net https://courses.lumenlearning.com/trident-boundless-chemistry/chapter/history-of-atomic-structure/ https://www.slideshare.net/mobile/JeromeJerome1/4-the-discovery-of-the-structure-of-the-atom https://i1.wp.com/www.compoundchem.com/wp-content/uploads/2016/10/The-History-of-the-Atom-–-Theories-and-Models.png?ssl=1 https://www.preceden.com/timelines/164909-timeline-of-the-evolution-of-the-atomic-theory
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