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Home , Atom, Atomic theory, Ernest Rutherford, Hans Geiger, John Dalton, Radiochemistry

Atomic Model Timeline

http://www.cs.utah.edu/~draperg/cartoons/jb/bohring.gif 400BC

Democritus found that are not all the same, they are eternal, and always moving. He made a on this to explain why and how atoms were so small, and what they were about. He proposed a more advance . http://www.philosophyprofessor.com/images/philosophers/democritus.jpg 400BC ish Indivisible, Sphere Model

Developed by Democritus. He said all is composed of indivisible tiny things made up into small not being able to be seen by the eye structures. 384-322BC and fellow Greeks

He found that matter is made of atoms. He also found that matter will always exist. He also found 4 elements, , , , and air. With all this, he came up with the theory of .

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

He had the first version of the Law of Conservation of Matter. He also named and . He invented the first , which had 33 elements.

http://www.seilnacht.com/Lexikon/lavoisi.JPG 1780 Charles Augustin de

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 to come up with this law.

http://www.bhak-bludenz.ac.at/physik/geschichte/physiker/bilder/coulomb.jpg 1803 John

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 and used 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

He came up with and . He investigated canal rays, cathode rays, and plasmas. He used in gases, and found as the went down, the electrodes began to emit rays. http://www.vanderkrogt.net/elements/images/portret/Crookes.jpg 1896

He came up with radioactivity. He found this out from unknown x-rays waves, which were produced by . Penetrating was also discovered by Becquerel. He also discovered that uranium was able to expose a photographic plate on paper, and didn’t depend on the chemical state.

http://dbhs.wvusd.k12.ca.us/webdocs/Gallery/Becquerel.GIF 1895 W.K.

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 . 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 and subatomic when he was working with tubes. He was working with glass tubes and electricity and messed up and discovered electrons.

http://www.phy.cam.ac.uk/cavendish/history//jj_c1890.jpg 1897

Discovered by J.J. Thomson. He said the was a sphere of positive electricity, with negative particles throughout. This came around right after he discovered the electron. 1898 Marie & Pierre

They both picked up on Becquerel’s work on uranium, which them to find the elements and . 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.” ~ http://www.neoam.cc.ok.us/~rjones/Pages/online1014//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

He was the person who came up with the original 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

First, he found that and matter intertwine somehow, the theory of measurement came about from this. Second, he publish 5 papers on electrons. These contributed to the . He said, “ 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

He helped invent the , and the Geiger-Marsden experiment led him to the discovery of the . The counter was able to prove the Compton effect, because is detected the , electrons, and quanta.

http://www.origin-life.gr.jp/2904/2904174/42.jpg 1911 Ernest

He ionized using radiation, and found alpha and beta waves. He used his research and the magnetic properties of 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 to find positive and negative charges in an atom.

http://www.newgenevacenter.org/portrait/rutherford.jpg 1913

Niels figured out the structure of the atom, and their . 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 1913 The

Niels Bohr discovered this atom. It shows a positively charged nucleus surrounded by electrons. This was mostly to explain the Rydberg . The Bohr model is a hydrogen model. It helps with the learning of the quantum theory.

http://en.wikipedia.org/wiki/Bohr_model 1920’s Electron Cloud Model

Discovered by Erwin Schrödinger and . They said an atom consists of a dense nucleus and many 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 out, he worked out math equations and used .

http://academic.brooklyn.cuny.edu/history/virtual/portrait/schroedinger.jpg 1932

James discovered the existence of the . 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 &

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 of . His biggest discovery was as a fission element. He combined results with Otto Frisch and they came up with . He was testing uranium and how it busted into lighter elements. Lise always studied radioactivity. She, herself, discovered the . 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 “” 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 who received a for his theory on elementary particles. He also found that all the elements of an atom are held together by . To find this, he blasted high speed electrons into a . 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 Bibliography http://en.wikipedia.org/wiki/Antonie_Lavoisier http://library.thinkquest.org/10170/voca/coulombb.htm http://scienceworld.wolfrom.com/biograhpy/Dalton.html http://en.wikipedia.org/wiki/William_Crookes www.atomicmuseum.com/tour/atomicage.cfm www.phy.hr/~dpaar/fizicari/xcurie.html http://en.wikipedia.org/wiki/J.J._Thomson http://en.wikipedia.org/wiki/Murray_Gell-Mann#Prizes http://scienceworld.wolfram.com/biography/Gell-Mann.html http://www.geocities.com/omegaman_uk/gellmann.html http://en.wikipedia.org/wiki/George_Zweig http://pdg.web.cern.ch/pdg/cpep/history/smt.html http://www.britannica.com/eb/article-9066466/Glenn-T-Seaborg http://en.wikipedia.org/wiki/Otto_Hahn http://en.wikipedia.org/wiki/Lise_Meitner http://www.childrenofthemanhattanproject.org/HF/Biographies%20-%20Men/chadwick.htm http://homepage.mac.com/tatara/nadesicops/nd_s_schrodinger.html http://library.thinkquest.org/15567/bio/schrodinger.html http://en.wikipedia.org/wiki/Niels_Bohr#Middle_years http://en.wikipedia.org/wiki/Bohr_model http://webpub.alleg.edu/employee/g/grodgers/ScientificTravelingWebsite/Rutherford.html http://micro.magnet.fsu.edu/optics/timeline/people/rutherford.html http://chem.ch.huji.ac.il/~eugeniik/history/millikan.html http://www.crystalinks.com/einstein.html http://home1.gte.net/vze3h8h7/id43.html http://periodictable.com/pages/AAE_Democritus.html http://www.fsmitha.com/h1/ch10.htm http://www.geocities.com/bioelectrochemistry/coulomb.htm http://antoine.frostburg.edu/chem/senese/101/atoms/dalton.shtml http://en.wikipedia.org/wiki/William_Crookes http://www.lbl.gov/abc/wallchart/chapters/02/1.html http://www.neoam.cc.ok.us/~rjones/Pages/online1014/chemistry/chapter_8/pages/histor y_of_atom.html#becquerel-curie%20anchor http://www.expage.com/atomproject http://www.akisrx.com/inglese/htm/roentgen.htm http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci332247,00.html www.watertown.k12.wi.us/4s/staff/buescher/atom/time.asp www.angelfire.com/mb2/atoms http://hi.fi.tripod.com/timeline http://www.csmate.colostate.edu/cltw/cohortpages/viney/atomhistory.html