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Democritus was one of the first to suggest that all matter was composed of tiny discrete particles that would become known as "atoms".
https://en.wikipedia.org/wiki/Democritus -
Plato also was one of the first people to suggest the universe was made of tiny particles, shaped like triangles.
https://en.wikipedia.org/wiki/Plato -
They believed all metals were made of 2 elements, mercury and sulfur. They discovered many elements including phosphorus and antimony but falsely believed they were combinations of mercury and phosphorus.
https://uwaterloo.ca/chem13-news-magazine/february-2019/feature/ancients-and-alchemists -
Boyle developed the scientific method and developed the law between a gases' volume and its pressure which showed that they were made of tiny particles, the atoms.
https://en.wikipedia.org/wiki/Robert_Boyle -
Antoine discovered Oxygen and Silicon. He also discovered the law of mass conservation, which meant that atoms could not be created or destroyed completely.
https://en.wikipedia.org/wiki/Antoine_Lavoisier -
The Billiard ball model was created by John Dalton in 1803. The model only consisted of the solid indivisible atom with no components, as the electron, neutron, and proton had not been discovered yet.
https://www.scienceabc.com/pure-sciences/dalton-atomic-model.html -
Avogadro created Avogadro's law and number. The law states that any gas that have the same temp, volume, and pressure have an identical amount of molecules. The number is the ratio of the atomic mass to mass in grams, it is roughly 6.022*10^23.
https://en.wikipedia.org/wiki/Amedeo_Avogadro -
Developed theory of atomism and atomic mass.
https://www.britannica.com/biography/John-Dalton -
Formed the periodic law and table; made a way to organize elements
https://en.wikipedia.org/wiki/Dimitri_Mendeleev -
JJ Thompson discovered the electron, the fundamental component of an atom and it's bonds
https://en.wikipedia.org/wiki/JJ_Thompson -
The plum pudding model was created by JJ Thomson in 1904. It portrays negatively charged particles floating without orbits in a positively charged soup of matter.
https://en.wikipedia.org/wiki/Plum_pudding_model -
Robert Millikan discovered the negative charge of an electron and the photoelectric effect, which is the ejection of electrons from an atom using a gamma ray.
https://en.wikipedia.org/wiki/Robert_Andrews_Millikan -
Rutherford discovered the nuclear structure of an atom, and also discovered alpha and beta rays. -
The Curies discovered the property of radioactivity along with elements polonium and radium. https://en.wikipedia.org/wiki/Marie_Curie -
Henry developed Mosley's lay which is the relationship between wavelengths of X-rays from metals and their atomic number
https://en.wikipedia.org/wiki/Henry_GJ_Mosely -
solar system model was created by Niels Bohr in 1913. It describes atoms as consisting of a positively charged nucleus surrounded by a number of electrons in orbits around that nucleus, similar to a solar system.
https://www.britannica.com/science/Bohr-model -
Albert Einstein made many advancements to the atomic theory including the mass-energy equivalence (E=M(C^2)) and theories of
https://en.wikipedia.org/wiki/Albert_Einstein -
Proposed the model of that atom in which electrons orbit around the nucleus, which is used to this day.
https://en.wikipedia.org/wiki/Niels_Bohr -
The electron cloud model was created by Erwin Schrödinger and Werner Heisenberg in 1926. It is used to visualize likely positions of electrons in an atom instead of actual orbits of electrons.
https://www.vedantu.com/question-answer/does-the-electron-cloud-model-describe-class-11-chemistry-cbse-60af1b83f4d76d18e8666f1c -
Heisenberg was the main pioneer of the theory of quantum mechanics, the theory of how subatomic particles behave, and discovered allotropic (alternate) forms of hydrogen.
https://en.wikipedia.org/wiki/Werner_Heisenberg -
Chadwick discovered the neutron, a fundamental component of the nucleus of an atom.
https://en.wikipedia.org/wiki/James_Chadwick -
Schrödinger was also a pioneer of quantum mechanics, famous for the thought experiment that a cat (particle) left in a box with a 50/50 chance that it would die (decay) would be in a superimposed state of being alive or dead until it would be observed, then it would "choose" a state
https://en.wikipedia.org/wiki/Erwin_Schrödinger