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500 BCE
The Alchemists
The Alchemists used Aristotle's ideas about matter to create experiments with goal of changing the structure of an item. Even though they were unsuccessful in their experiments, this scientific process will eventually lead people to finding atoms. healthresearchfunding.org/alchemists-atomic-theory-explained/ -
427 BCE
Plato
Plato was a famous philosopher who introduced an atomic theory in which atoms had ideal geometric forms, and each form represented either air, earth, fire, or water. philosophy-question.com/library/lecture/read/5093-how-did-galileo-prove-aristotle-wrong#5 -
400 BCE
Democritus
Democritus developed Leucippus' theory of atoms that stated that all matter is made out of atoms. He was one of the first people to promote this theory. reference.com/science/did-democritus-contribute-atomic-theory-4653045c78e24bd4 -
Robert Boyle
Robert Boyle stated that atoms must exist based on the relation between volume of gas and pressure. famousscientists.org/robert-boyle/
refences.com/science/robert-boyle-s-contribution-atomic-theory-2933c73ad42cc70b -
Antone Lavoisier
Antone Lavoisier created the Law of Conservation of Mass (all matter cannot be created not destroyed, and is made up out of atoms). Also, he how atoms react in the chemical reaction. wikilivre.org/culture/when-did-antone-lavoisier-contribute-to-the-atomic-theory/#When_did_Lavoisier-contribute_to_the _atomic_theory -
John Dalton
John Dalton developed methods to calculate atomic weight. He also created his own atomic theory and symbolized atoms. sidmartinbio.org/what-are-the-contributions-of-john-dalton/#What_are_the_contributions_of_John_Dalton -
Billiard Ball Model
Created by John Dalton, the Billiard Ball Model represents atom as a ball-like structure, showing that atoms have no nucleus, nor any electrons! https://brilliant.org/wiki/daltons-atomic-model/ -
Amedeo Avogadro
Amedeo Avogadro hypothesize that equal volumes of gases at the same temperature and pressure contain equal amount of molecules (contains two or more atoms). He came up with the hypothesis from the conclusion he made from the experiment with oxygen, which said that oxygen atom split in two from forming vapor. sciencehistory.org/historical-profile/amedeo-avogadro -
Dmitri Mendeleev
Dmitri Mendeleev was a famous Russian chemist who published the first periodic table of elements that was excepted in the scientific community. This periodic table was sorted by their chemical properties and a relative atomic mass. https://www.reference.com/science/mendeleev-s-contribution-atomic-theory-published-178e33fa71abb03e
https://www.thoughtco.com/who-invented-the-periodic-table-608823 -
J.J. Thomson
A British physicist called J.J. Thomson was the first ever person to claim that the basic body of the atom is spherical in shape and contains subatomic particles, which were called electrons. Therefore, JJ Thomson discovered electrons. geeksforgeeks.org/thomsons-atomic-model/ -
Pierre and Marie Curie
Maire Curie and Pierre Curie worked with the mysterious (for that time) power found in the atom called radiation. The countless experiments and contributions of these two physicists helped people understand the entity that atom can be split to release enormous amount of energy. pages.mtu.edu/~pcharles/SCIHISTORY/Marie_Curie.html#:~:text -
Plum Pudding Model
Created by J.J. Thomson, the Plum Pudding Model shows how the atom consists of sphere of positive charge within which electrostatic forces determined the positioning of the negatively charged corpuscles, hence explaines the neutral charge of the atom. He named his model after an association: the corpuscles in the positive charge reminded Thomson plums in pudding. https://www.periodic-table.org/what-is-thomson-model-of-the-atom-plum-pudding-model-definition/ -
Albert Einstein
A German-born theoretical physicist Albert Einstein published an analysis in which he found a way to predict the size of atoms by using mathematics, proving the existence of the atom. reference.com/science/did-einstein-contribute-atomic-theory-2e013425c0d5fb9e -
Robert Millikan
Robert Millikan was an American physician who found a precise way of finding the weight of an electron using an experiment called 'oil drop experiment'. nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/pioneers/robert-millikan -
Neils Bohr
Niels Bohr was famous for his creation of the most widely accepted model of the atom. atomicheritage.org/profile/niels-bohr -
Ernest Rutherford
Ernest Rutherford discovered that most of the atom's mass is located in a dense region, which he called nucleus. He found the nucleus by the experiment he used called 'gold foil experiment'. askingthelot.com/what-did-rutherfords-gold-foil-experiment-reveal-about-atoms-atomic-structure/ -
Solar System Model
The Solar System Model of the atom was created by Niels Bohr, who believed that all electrons exist on its own orbit, each having a different distance from the nucleus. Electrons fly around the nucleus on their orbits just like our planets around the Sun, hence the name of this model. -
Henry G. J. Moseley
Henry Moseley was an English physicist who stated that the atomic number on the periodic table is the number of the positively charged particles in the nucleus of the atom. britannica.com/biography/Henry-Moseley -
Erwin Schrodinger
Erwin Schrodinger was an Austrian physicist who created an equation that could calculate the quantization of the hydrogen atom's energy levels- waves- in the Niels Bohr's model of the atom. The calculation would show how the wave function of the electron evolves. https://www.britannica.com/biography/Erwin-Schrodinger -
Electron Cloud Model
The Electron Cloud Model was created off of Erwin Schrodinger's belief that electrons are some sort of waves, which travel in rapid motion - not around the nucleus in a fixed orbit. Schrodinger stated that the scientists could only make educational guesses in an attempt to position the electrons when using this model. https://www.sidmartinbio.org/who-created-the-electron-cloud-model/ -
Werner Heisenberg
A German theoretical physicist called Werner Heisenberg calculated the behavior of electrons around the atom with the Uncertainty Principle. His achievements helped clarify amount of electrons to find how many the atom contains. werner-heisenberg.weebly.com/contribution-to-the-atom.html -
James Chadwick
James Chadwick British physicist discovered reactions in the nucleus of the atoms by using radioactive particles. atomictheoryfinal.weebly.com/james-chadwick.html
