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Period: 300 to
timeline
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340
Aristotle
Aristotle proposed that all Atoms were made up of Air, Fire, Water and Earth. He disregarded the idea that Leucippos and his disciple Democritus had of all matter being composed of tiny particles. Aristotle had no experiment as he was only a theorist. The image represents Aristotle's view on matter, and his contribution to the development of the Atom was that he intrigued others to try and look for better insight regarding the Atom, albeit his theory being wrong. Aristotle studied at Athens. -
340
Aristotle image
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450
Leucippos/Democritus
Leucippos and his student Democritus both theorized that if you keep cutting a piece of solid matter you will eventually end up with a particle so small that it could not be cut anymore. Democritus called this the "Atomos". The two did not have any experiments as they were only theorists and did not have a specific idea on what the atom actually looked like. These two contributed to the development of the atom as their theory was the first building block. Both of them studied at Athens. -
450
Leucippos image
Leaucippos -
Robert Boyle
Robert Boyle published his book named “The Sceptical Chymist” which outlined what we now call the scientific method. Boyle did not have a specific description of an atom but did disregard Aristotle’s theory and provide a definition for an Element as he called it an “unmingled body”. Boyle discovered new elements with basic chemical experiment\s and his corpuscularism ideology. His experiments were mostly in England and his contribution is significant as he paved the path for the periodic table. -
John Dalton
Influenced by the work of scientists such as Carl Scheele, John Dalton was lead to develop his Atomic Theory which he presented in his book “A New System of Chemical Philosophy”. His theory outlined the properties of Atoms, the way they combine, and how they act in a reaction. Dalton described an Atom as a small sphere and his contribution to the atom was ground-breaking as his work influenced the modern atomic theory. The picture shows his Atom and he experimented in an English college. -
John Dalton image
John Dalton -
William Crookes
Working alongside other scientists, William Crookes was able to lead to the discovery of the Electron. In his glass tube experiment he was able to discover a stream of particles travelling from cathode to anode when all of the air was pumped out of the system. He theorized that the particles were negatively charged. He contributed to the Atom as his work directly lead to the Electron. Crookes description of the Atom was the same as Dalton's. The picture is his experiment and he worked in England -
Max Planck
Max Planck came up with the quantum theory which proposed that energy could behave like particles in the form of tiny packets known as quanta. His equation for determining the energy associated with quanta was E=HV known as “Planck’s Constant”. He contributed to the Atom as his work helped Niels Bohr rectify Rutherford’s Atomic model, and helped Einstein explain photoelectric effect. His idea of the Atom was the same as Dalton's as the Electron was only accepted in 1906 and he worked in Berlin. -
J.J Thomson
By modifying William Crookes’ glass tube to focus a cathode ray into a triangle and exposing to certain fields, J.J Thompson was able to prove the existence of the Electron and determine its size in comparison to a Hydrogen ion. He also speculated on the existence of a Proton. His contribution was great to the atom as he validated the Electron, gave segue to the Proton, and his Atomic model was a great advance. He described an Atom as plum pudding with Electrons as plums. He worked in England. -
J.J Thomson image
J.J Thomson -
Albert Einstein
Albert Einstein proved skeptics towards Max Planck’s Quantum theory wrong. He was able to use the Quantum theory in one of his papers to explain the “photoelectric effect”. Einstein proved Atoms exist through his explanation of the Brownian Motion. His equation E=MC2 also lead to a deeper understanding of Atomic relations. He contributed to the Atom as his work unraveled the atomic structure and technologies enhanced. His view of the Atom was similar to Rutherford’s and he worked in New Jersey. -
Ernest Rutherford
As one of J.J Thompson’s students, Ernest Rutherford tested his teacher’s atomic model. He did this by bouncing off Alpha particles on gold foil and when he got erratic results, it lead to him discovering the Nucleus in which particles both positively and neutrally resided. His contribution to the Atom is great as it lead to a better understanding of atomic structure and subatomic particles. His description of the Atom involved Electrons circling the Nucleus. He worked in the United Kingdom. -
Ernest Rutherford image
Ernest Rutherford -
Niels Bohr image
Niels Bohr -
Niels Bohr
Niels Bohr saved Rutherford’s theory and explained the Bright-line spectrum with his work. Bohr expanded on Rutherford’s theory by suggesting Electrons occupied energy levels, Suggesting how Electron transition involved energy, and how Electron transition=color change. All of this lead to the Bohr diagram. Contribution improved atom models and saved Rutherford’s theory. Description of the atom is the same as Rutherford’s except it involved energy levels. He worked in Copenhagen mostly. -
James Chadwick
Even after the discovery of Electrons and Protons many researchers including James Chadwick agreed that there was another particle adding to the Atom’s mass but not charge. Chadwick took the methods of Irene and Joseph Joliot Curie for tracking particle radiation and found the Neutron. His contribution for the Atom was so significant because he found the final piece to the puzzle of the Atom. His vision of the Atom was modern; Electrons around the finalized Nucleus. He worked in the U.K -
James Chadwick image
James Chadwick
