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440 BCE
Plato
Proposed that a fifth atomic type must exist which was later called "ether" and developed a wide-ranging philosophical system (platonism) -
400 BCE
Democritus
Determined the magnitude of an electron's charge https://www.google.com/search?q=how+did+democritus+contribute+to+the+atomic+theory -
Robert Boyle
Defined the modern idea of an element and introduced many standard chemical tests https://www.bbc.co.uk/history/historic_figures/boyle_robert.shtml#:~:text=It%20is%20Boyle's%20Law%20for,'corpuscular%20theory'%20of%20chemistry. -
Antoine Lavoisier
Found that the total mass of products and reactants in a chemical reaction stay the same https://www.breakingatom.com/learn-the-periodic-table/the-history-of-the-atomic-model-lavoiser-and-dalton#:~:text=A%20later%20breakthrough%20in%20the,law%20of%20conservation%20of%20mass. -
Billiard Ball Model
Founded by John Dalton
https://www.ck12.org/chemistry/daltons-atomic-theory/lesson/Daltons-Atomic-Theory-MS-PS/ -
The Alchemist
Laid down the foundation of the Modern Day Periodic Table https://prezi.com/t50cihtay12m/alchemy-and-its-contributions-to-the-atomic-theory/ -
John Dalton
Proposed that all matter was made of atoms and that chemical reactions resulted in the rearrangement of reacting atoms https://courses.lumenlearning.com/introchem/chapter/john-dalton-and-atomic-theory/#:~:text=Dalton's%20atomic%20theory%20proposed%20that,indivisible%20and%20indestructible%20building%20blocks.&text=Dalton%20also%20postulated%20that%20chemical,rearrangement%20of%20the%20reacting%20atoms -
Amedeo Avogadro
Hypothesized that equal volumes of different gases contain an equal number of molecules https://www.famousscientists.org/amedeo-avogadro/#:~:text=Amedeo%20Avogadro%20is%20best%20known,the%20same%20temperature%20and%20pressure.&text=Avogadro%20was%20also%20the%20first,rather%20than%20as%20individual%20atoms. -
Dmitri Mendeleev
Devised the periodic classification of the chemical elements; elements are arranged in order of increasing atomic weight https://www.britannica.com/biography/Dmitri-Mendeleev -
JJ Thomson
Showed that all atoms contain negatively charged electrons https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/a/discovery-of-the-electron-and-nucleus#:~:text=Summary-,J.J.,positively%2Dcharged%20%22soup.%22 -
Plum Pudding Model
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Pierre and Marie Curie
Theorized that uranium rays came from the element's atomic structure https://www.britannica.com/science/atom/Discovery-of-radioactivity -
Albert Einstein
Mathematically proved the existence of atoms https://www.ans.org/news/article-969/albert-einstein-and-the-most-elemental-atomic-theory/#:~:text=Einstein%20also%20in%201905%20mathematically,use%20of%20statistics%20and%20probability.&text=Atomic%20theory%20says%20that%20any,always%20in%20random%2C%20ceaseless%20motion. -
Robert Millikan
Determined the magnitude of an electron's charge https://www.nobelprize.org/prizes/physics/1923/millikan/facts/ -
Ernest Rutherford
Found that the atom consists mostly of empty space with its mass concentrated in the nucleus https://www.britannica.com/biography/Ernest-Rutherford -
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Neils Bohr
Proposed that some physical quantities only take discrete values https://www.nobelprize.org/prizes/physics/1922/bohr/facts/ -
Henry G. J. Mosely
Used self-built equipment to prove that every element's identity is determined by the amount of protons it has https://www.famousscientists.org/henry-moseley/#:~:text=In%201913%20he%20used%20self,all%20of%20which%20were%20found. -
Erwin Schrodinger
Used mathematical equations to describe the likelihood of finding an electron in a certain position http://www.abcte.org/files/previews/chemistry/s1_p6.html#:~:text=In%201926%20Erwin%20Schr%C3%B6dinger%2C%20an,mechanical%20model%20of%20the%20atom. -
Electron Cloud Model
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Werner Heisenberg
Formulated quantum mechanics in terms of matrices https://www.britannica.com/biography/Werner-Heisenberg -
