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Democritus broke a shell in half and broke a piece in half over and over until he couldn’t anymore and realized he’d found indivisible pieces of life.
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He performed quantitative experiments that demonstrated to role of oxygen in combustion and metal calcination, ending phlogiston theory and Greek four element theory. He also named oxygen in 1778 and hydrogen in 1783
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Developed by Antoine Lavoisier
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He experimented with gasses to discover total pressure of gaseous mixture is sum of partial pressures each gas exerts while in same space.
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The theory states all matter is composed of atoms, indivisible and indestructible building blocks and all atoms are identical, but different elements have atoms of differing size and mass.
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Mendeleev realized physical and chemical properties were related to atomic mass of elements in a periodic manner. He also corrected known the atomic masses and predicted properties of elements he didn't even know to exist.
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His most important experiment was putting two oppositely charged electric pates in a cathode ray tube to discover the cathode ray was composed of negatively charged particles. Thomson determined mass-to-charge ratio of cathode ray particles
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Scientists discovered something was traveling from the anode because a shadow was cast on a glowing wall.
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Developed by J.J. Thomson
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It measured the angle that a particle’s scattered after going through thin metal foil. It took 5 years starting in '08 for Rutherford to complete the experiment
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He developed the oil drop experiment that measured the charge present to droplets in oil mist. It proved the force on any charge in the field is the product of charge and electric field. Millikan measured both electric force and magnitude of electric field.
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The most important thing Rutherford did was develop the gold foil experiment.
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Created by Niels Bohr
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Bohr established a theory about how energy is transferred in defined quantities and electrons move around the nucleus in prescribed orbits to keep them from losing energy and spiraling into the nucleus.
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X-ray radiation has a precise mathematical relationship with atomic numbers
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Used mathematical equations to take the Bohr model even further and, with Werner Heisenberg, determined regions in which electrons would most likely be found
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Created by Erwin Schrödinger
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Created by Erwin Schrödinger and Werner Heisenberg
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Using head on elastic collision, scientists saw the energy given off was greater than a nucleus could do so Chadwick determined it was a neutral particle, not a photon and tested it on nitrogen, oxygen, helium, and argon
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1) http://thelittleguy22.tripod.com/id1.html#:~:text=%22Atoms%22%20in%20Greek%20means%20%22,and%20break%20it%20in%20half.
2) https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/a/discovery-of-the-electron-and-nucleus
3) https://www.biography.com/scientist/john-dalton#:~:targetText=Dalton's%20experiments%20on%20gases%20led,Dalton's%20Law%20of%20Partial%20Pressures. -
4) http://chemed.chem.purdue.edu/genchem/history/gold.html
5) https://courses.lumenlearning.com/boundless-chemistry/chapter/discoveries-leading-to-nuclear-atom-model/#:~:targetText=Cathode%20rays%20carry%20electronic%20currents,which%20he%20called%20%E2%80%9Celectrons.%E2%80%9D
6) http://chemed.chem.purdue.edu/genchem/history/lavoisier.html
7) https://www.beautifulchemistry.net/lavoisier
8) https://www.britannica.com/biography/Robert-Millikan -
9) https://www.britannica.com/science/Millikan-oil-drop-experiment
10) https://www.atomicheritage.org/profile/james-chadwick
11) http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/neutrondis.html#:~:targetText=Discovery%20of%20the%20Neutron,mass%20of%20this%20neutral%20particle.&targetText=This%20analysis%20follows%20that%20for,a%20much%20more%20massive%20one. -
12) http://www.abcte.org/files/previews/chemistry/s1_p6.html#:~:targetText=In%201926%20Erwin%20Schr%C3%B6dinger%2C%20an,mechanical%20model%20of%20the%20atom.
13) https://www.nobelprize.org/prizes/physics/1922/bohr/facts/#:~:targetText=In%201913%2C%20Niels%20Bohr%20proposed,but%20only%20in%20prescribed%20orbits.&targetText=Bohr's%20theory%20could%20explain%20why%20atoms%20emitted%20light%20in%20fixed%20wavelengths.
14) http://abyss.uoregon.edu/~js/glossary/bohr_atom.html -
15) https://www.msnucleus.org/membership/html/jh/physical/atomictheory/lesson1/atomic1g.html
16) https://courses.lumenlearning.com/introchem/chapter/john-dalton-and-atomic-theory/#:~:targetText=Dalton's%20atomic%20theory%20proposed%20that,of%20differing%20size%20and%20mass.
17) https://corrosion-doctors.org/Periodic/Periodic-Mendeleev.htm
18) https://www.khanacademy.org/partner-content/big-history-project/stars-and-elements/knowing-stars-elements/a/dmitri-mendeleev -
