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500 BCE
The Alchemists
The Alchemists used Aristotle's idea about matter and began to create experiments with his ideas. They also contributed to the theory because of their studies of natural processes. https://healthresearchfunding.org/alchemists-atomic-theory-explained/ -
428 BCE
Plato
Plato's cosmology comes from a mathematical discovery by Empedocles. http://abyss.uoregon.edu/~js/glossary/plato.html -
400 BCE
Democritus
Democritus Said all matter was formed of different types of tiny discrete particles and that the properties of these particles determined the properties of matter. https://www.ccp5.ac.uk/sites/www.ccp5.ac.uk/files/Democritus/Basic/Atheory.html#:~:text=About%20400%20B.C.%20the%20Greek,determined%20the%20properties%20of%20matter. -
Solar System Model
Galileo used his telescoped to prove the sun in the middle of the solar system and not the earth. He then creaated a model of the solar system called the Heliocentric model. https://spacecentre.co.uk/blog-post/galileos-telescope-changed-our-view-of-the-solar-system/#:~:text=The%20discoveries%20that%20Galileo%20made,by%20astronomers%20like%20Nicolaus%20Copernicus. -
Robert Boyle
Boyle Contributed to the atomic theory by his law which states that the volume of gas decreases with increasing pressure and the other way around/vice versa. https://www.bbc.co.uk/history/historic_figures/boyle_robert.shtml#:~:text=It%20is%20Boyle's%20Law%20for,'corpuscular%20theory'%20of%20chemistry. -
Antoine Lavoisier
Lavoisier found that mass is conserved in a chemical reaction. http://chemed.chem.purdue.edu/genchem/history/lavoisier -
John Dalton
Dalton published his first general account of chemical atomic theory. https://pubmed.ncbi.nlm.nih.gov/18175369 -
Billiard Ball Model
John Dalton invented the Billiard Ball Model. He thought atoms were the smallest particles of matter, he saw them as solid, hard spheres, like billiard balls, so he used wooden balls to model them. https://www.ck12.org/chemistry/daltons-atomic-theory/lesson/Daltons-Atomic-Theory-MS-PS/#:~:text=Because%20Dalton%20thought%20atoms%20were,pictured%20in%20the%20Figure%20below. -
Amedeo Avogadro
Avogadro hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. https://www.sciencehistory.org/historical-profile/amedeo-avogadro -
Dmitri Mendeleev
Jotted down symbols for the chemical elements, putting them in order according to their atomic weights and inventing the periodic table. https://www.newscientist.com/people/dmitri-mendeleev -
JJ Thompson
Thompson Discovered that atoms were made up of smaller components like neutrons, electrons, and protons. https://www.history.com/this-day-in-history/jj-thomson-announces-discovery-of-electrons -
Plum Pudding Model
The Plum Pudding Model is one scientific model of the atom introduced by JJ Thompson. He proposed this after his discovery of the electron. https://www.universetoday.com/38326/plum-pudding-model/ -
Pierre and Marie Curie
They successfully isolate radioactive radium salts from the mineral pitchblende in their laboratory in Paris. https://www.history.com/this-day-in-history/curies-isolate-radium -
Albert Einstein
Einstein mathematically proved the existence of atoms which helped revolutionize all the sciences through the use of statistics and probability. https://www.ans.org/news/article-969/albert-einstein-and-the-most-elemental-atomic-theory -
Ernest Rutherford
Rutherford discovered the atomic nucleus. https://www.aps.org/publications/apsnews/200605/history.cfm -
Niels Bohr
Bohr proposed a theory for the hydrogen atom, based on a quantum theory. https://www.nobelprize.org/prizes/physics/1922/bohr/facts/ -
Robert Millikan
Millikan's famous oil drop measured the fundamental unit of electric charge. https://www.aps.org/publications/apsnews/200608/history.cfm -
Henry G. J. Moseley
Moseley published a paper in which he concluded that the atomic number is the number of positive charges in the atomic nucleus. https://www.britannica.com/biography/Henry-Moseley -
Erwin Schrödinger
Schrödinger formulated a wave equation that accurately calculated the levels of the energy of electrons. https://www.nobelprize.org/prizes/physics/1933/schrodinger/facts/ -
Electron Cloud Model
The electron cloud model proposed by Erwin showed people that electrons were no longer seen as moving particles around the nucleus of an atom, so he made an educated guess to where they were. https://www.universetoday.com/38282/electron-cloud-model/#:~:text=One%20such%20example%20is%20the,to%20the%20positions%20of%20electrons. -
Werner Heisenburg
Werner Heisenberg developed a key piece of quantum theory. https://www.aps.org/publications/apsnews/200802/physicshistory.cfm -
James Chadwick
Chadwick reports his discovery of the neutron.
