Atomic Model Timeline http://www.cs.utah.edu/~draperg/cartoons/jb/bohring.gif
400BC Democritus Democritus found that atoms are not all the same, they are eternal, and always moving. He made a theory on this to explain why and how atoms were so small, and what they were about. He proposed a more advance atomic theory. http://www.philosophyprofessor.com/images/philosophers/democritus.jpg
400BC ish Indivisible, Solid Sphere Model Developed by Democritus. He said all matter is composed of indivisible tiny things made up into small not being able to be seen by the eye structures.
384-322BC Aristotle and fellow Greeks He found that matter is made of atoms. He also found that matter will always exist. He also found 4 elements, fire, water, earth, and air. With all this, he came up with the theory of motion. http://img.tfd.com/authors/aristotle.jpg
500BC-1720 Alchemists Now, they wanted to live forever, so they started out with trying to make a potion that could make them live forever. They didn t succeed, but they did make many experiments, and the scientific method. They also kept careful records.
1777 Antoine Lavoisier He had the first version of the Law of Conservation of Matter. He also named oxygen and hydrogen. He invented the first periodic table, which had 33 elements. http://www.seilnacht.com/lexikon/lavoisi.jpg
1780 Charles Augustin de Coulomb He had the theory of Simple Machines. He also had Coulomb s law which stated the interaction between electric charges. He also published the laws of friction. He used windmills and the elasticity of fibers and metals to come up with this law. http://www.bhak-bludenz.ac.at/physik/geschichte/physiker/bilder/coulomb.jpg
1803 John Dalton He proposed the atomic theory. He inferred proportions of elements in compounds. He found the atomic weight, and chemical symbols. He also had the most useful atomic theory of matter. To come up with this, he tested gases and used evaporation to find out what the gases had on that mixture all together. http://redescolar.ilce.edu.mx/redescolar/efemerides/septiembre2001/interna/dalton.gif
1879 Sir William Crookes He came up with thallium and helium. He investigated canal rays, cathode rays, and plasmas. He used electricity in gases, and found as the pressure went down, the electrodes began to emit rays. http://www.vanderkrogt.net/elements/images/portret/crookes.jpg
1896 Becquerel He came up with radioactivity. He found this out from unknown x-rays waves, which were produced by uranium. Penetrating radiation was also discovered by Becquerel. He also discovered that uranium was able to expose a photographic plate on black paper, and didn t depend on the chemical state. http://dbhs.wvusd.k12.ca.us/webdocs/gallery/becquerel.gif
1895 W.K. Roentgen He discovered x-rays when he was working with Sir William Crooke s tube. He also found that x-rays pass through different materials at different temperatures. He was doing an experiment on cathode rays, when he messed up and discovered x-rays. http://hi.fi.tripod.com/timeline/images/wilhelm_rontgen.jpg
1897 J.J. Thomson He found electrons and subatomic particles when he was working with cathode ray tubes. He was working with glass tubes and electricity and messed up and discovered electrons. http://www.phy.cam.ac.uk/cavendish/history/electron/jj_c1890.jpg
1897 Plum Pudding Model Discovered by J.J. Thomson. He said the atom was a sphere of positive electricity, with negative particles throughout. This came around right after he discovered the electron.
1898 Marie & Pierre Curie They both picked up on Becquerel s work on uranium, which lead them to find the elements radium and polonium. Though Marie went further with the radioactivity of elements, she didn t get very far. All she said was, they were somehow disintegrating over time and emitting radiation that exposed the plate. ~ Marie Curie http://www.neoam.cc.ok.us/~rjones/pages/online1014/chemistry/chapter_8/pages/history_of_atom.html#becquerel-curie%20anchor Pierre went on to say that atoms might be composed of even smaller things. http://www.aip.org/history/curie/images/photos/0203-matte.jpg
1900 Max Planck He was the person who came up with the original quantum theory. To come up with this, all he did was research from pervious scientists and a little bit on his own, and then wrote a book on the quantum theory (the theory: the behavior or matter and energy in an atom). He also was looking at color changes from energy. He also made a math equation to help with this theory. http://www.spaceandmotion.com/images/planck-max-quantum-1.jpg
1905 Albert Einstein First, he found that nature and matter intertwine somehow, the theory of measurement came about from this. Second, he publish 5 papers on electrons. These contributed to the quantum mechanics. He said, light consists of quanta, bundles of energy which behave somewhat like particles. ~Albert Einstein http://www.crystalinks.com/einstein.html http://www.lucidcafe.com/library/96mar/96margifs/einstein.gif
1908 Robert Millikan He was by far the most famous American scientist. He wanted to find the electrical charge of electrons. He measured water droplets, and that wasn t successful, so he measured oil droplets, where all this proved electrons were negatively charged. He also was a professor for many years, and wrote many textbooks on chemistry. http://www.chemistryexplained.com/images/chfa_03_img0536.jpg
1908 Hans Geiger He helped invent the Geiger Counter, and the Geiger-Marsden experiment led him to the discovery of the atomic nucleus. The counter was able to prove the Compton effect, because is detected the neutrons, electrons, and quanta. http://www.origin-life.gr.jp/2904/2904174/42.jpg
1911 Ernest Rutherford He ionized gas using radiation, and found alpha and beta waves. He used his research and the magnetic properties of iron to find radio waves. He also discovered the atomic nucleus using others research and findings. To find this he did the Rutherford experiment. Briefly, he used a thin foil made of gold metal to find positive and negative charges in an atom. http://www.newgenevacenter.org/portrait/rutherford.jpg
1913 Niels Bohr Niels figured out the structure of the atom, and their radiations. He also discovered the principle of complementary. He introduced electrons from the book he wrote on the structure of the atom. He also started the basis of the quantum theory. http://www.nrc-cnrc.gc.ca/education/elements/images/elements/bohrium.jpg
Niels Bohr discovered this atom. It shows a positively charged nucleus surrounded by electrons. This was mostly to explain the Rydberg formula. The Bohr model is a hydrogen model. It helps with the learning of the quantum theory. 1913 The Bohr Model http://en.wikipedia.org/wiki/bohr_model
1920 s Electron Cloud Model Discovered by Erwin Schrödinger and Werner Heisenberg. They said an atom consists of a dense nucleus and many proton and neutrons and is surrounded by electrons, but they all have different energy levels, and different charges.
1922 Planetary or Solar System Model Both Rutherford and Bohr contributed into this model. Rutherford said the atom is mostly empty space with a nucleus that has a positive charge surrounded by negative electrons. Then Bohr said they circulate the atom.
1926 Erwin Schrödinger Erwin s contributions were the wave mechanics and quantum mechanics. He wrote papers on wave mechanics, which lead him to the quantum mechanics. To find these theories out, he worked out math equations and used statistics. http://academic.brooklyn.cuny.edu/history/virtual/portrait/schroedinger.jpg
1932 James Chadwick James discovered the existence of the neutron. He found this out because when he was looking at alpha waves, bounced off, saying there was no charge in the neutron. He also used an experiment similar to this to help with the creation of the atomic bomb, and the fission and uranium 235. http://www.nuclearfiles.org/images/library/biographies/bio_chadwick-james.jpg
1938 Otto Hahn & Lise Meitner While working in a lab, Otto Hahn discovered radiothorium, and then later discovered 5 more elements. He also discovered radioactive recoil. Lise Meitner was he partner when they discovered the isotope of protactinium. His biggest discovery was barium as a fission element. He combined results with Otto Frisch and they came up with nuclear fission. He was testing uranium and how it busted into lighter elements. Lise always studied radioactivity. She, herself, discovered the auger effect. http://cdl.niedersachsen.de/blob/images/c2710720_l20.jpg http://www.atomicmuseum.com/tour/photos/te-lm.jpg
1951 Glenn T. Seaborg Glenn was best known for identifying and discovering elements that were heavier then uranium. He also isolated 10 elements. He also proposed the actinides in the element table. He discovered these elements just by separating different elements, and combining different elements. http://www.radiochemistry.org/nuclearmedicine/pioneers/images/seaborg_g.jpg
1964 Murray Gell-Mann & George Zweig Murray Gell- Mann was an American physicist who received a Nobel Prize for his theory on elementary particles. He also found that all the elements of an atom are held together by quarks. To find this, he blasted high speed electrons into a hydrogen atom. George Zweig proposed the existence of quarks. He thought of them as aces, because he guessed there were four quarks in every atom. Now, in the same year, both these guys proposed the idea of quarks. They tested electrical charges, and that how the numbers for quarks came about. http://www.profes.net/rep_imagenes/monograf/nf1990a.jpg http://panda.unm.edu/images/people/faculty/gell_mann_murray.jpg
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