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Atomic Theory Scientists

Timeline created by lorraine in Science and Technology
Event Date: Event Title: Event Description:
Ymacakwvq66ca92c2mtcakd7nb3cavf5ktucach68p5ca3v9l88caqp9g1hca1nglc4ca0vn0jpcark8i0qca7og267caw83hagca24qfrlca81bh2pcacw6pmzcaofidq2cavy3axccawqusf9 small square 1st Jan, 0460 Democritus 460 BC Greece He developed the idea of atoms. He thought that at some point, a substance wouldn’t be able to be split in half anymore and he called these basic matter particles ‘atoms’. Without this idea of atoms, none of the discoveries of atoms or elements would have been made since they didn’t have a base to work on. http://www.nobeliefs.com/atom.htm
Images small square Isaac Newton 1704 England The book “Opticks” was released. It included context about atoms and forces between atoms. All change is caused by collisions of atoms. This showed that atoms could move and cause things to move as well. www.phys.virginia.edu/classes/252/atoms.html http://www.spaceandmotion.com/Physics-Sir-Isaac-Newton.htm
Es small square John Dalton 1803 England He started using symbols to represent the atoms of different elements. The logbook entry called Observations on the Ultimate Particles of Bodies and their Combinations had the first use of symbols to represent the elements in modern chemistry. Soon, he had a table of elements arranged by atomic mass. We can easily determine an element by the symbol and we know that they have different atomic masses. http://www.wired.com/science/discoveries/news/2008/09/dayintech_0903
Image small square George Johnstone Stoney 1894 Ireland He wrote a letter titled Of the “Electron”, or Atom of Electricity to the editors of the Philosophical magazine. He calls a definite quantity of electricity E¬r which is later developed to be an ‘electron’. Also, he estimates the mass of an electron. We know the mass on an electron and that it is a definite quantity of electricity. www.chemteam.info/Chem-History/Stoney-1894.html http://particleadventure.org/other/history/sciencet.html
Fdycaafh5rycak5rsm4cah1iz9mca8u5au3ca0t0qtacar8u6l9caebawdccajf9p2ucajv1g9ecagawfiacazxnl6kcavqgg76cab87l2dcad3kej5caeolwphca5bihdqcat5e8teca4t7vf7 small square Joseph John Thomson 1897 England He discovered that atoms contained electrons through his explorations on the properties of cathode rays. He concluded that the rays were composed of very light, negatively charged particles. We now know that an atom contains electrons and we know the structure of an electron cloud and how many electrons each shell of the cloud can hold. http://en.wikipedia.org/wiki/J._J._Thomson
Images1 small square Max Planck 1900 Germany He developed the Quantum theory. He attempted to draw conclusions from the heat radiation to the radiating atom. The discovery of quanta changed the idea of physics, because it showed that established ideas about the nature of radiation and energy were wrong. www.spaceandmotion.com/quantum-theory-max-planck-quotes.htm http://www.thebigview.com/spacetime/quantumtheory.html
Dfxca52tbwsca0rg6iacafwrl98catd91wtca50wtxjcas8865ycac3l2jzcasymovecatpky1ycavw5ae2ca8q8aikca7z41mbcaxiwfldca3cbvfycaegatfccan83j5zcauhv33hca5b2qay small square Hantaro Nagaoka 1903 Japan He was the first scientist to present a Saturnian model of an atom. The model displayed a nucleus containing positive electric charge and electrons ‘orbiting’ it. It gave us an idea of what an atom looked like, making it easier to understand the structure of it. http://www.japanese-greatest.com/technology/atomic-model.html
Dshcaerld6dcafjfchccafkcmbfcafuubrfcah0t0hbca7todflcajk1qrfcancaco9ca74q9j1caawxct9caqddr97cafpzosocar3cwllcap44ds8caew2t2fcaq863cucaidxty2ca06ehil small square Robert Andrews Millikan 1909 United States of America He worked on an oil-drop experiment which they used to measure the charge on an electron. The experiment was conducted by using charged oil droplets and suspending it between two metal plates. Since the electric field was known, the charge on the oil drops could be determined when the drops are held at a stable position. We are able to measure the charge of a single electron as a result of his experiment. http://en.wikipedia.org/wiki/Robert_Andrews_Millikan http
Rutherford small square Ernest Rutherford 1911 England He made up the Rutherford model, stating that a very small positively charged nucleus was orbited by electrons. It supported Nagaoka’s model of the atom. http://en.wikipedia.org/wiki/Ernest_Rutherford
Moseley small square Henry Gwyn Jefferys Moseley 1914 England He found a relationship between and element’s X-ray length and its atomic number. Before he discovered this, the atomic numbers were just sequential numbers based on the element’s atomic weight. It showed that there was a gap between atomic numbers 43 and 61 in the table. It shows that the atomic numbers of the elements aren’t just numbers based on the element’s weight but has connection with the element’s X-ray length. http://www.lycos.com/info/henry-moseley--elements.html http
Bohr small square Niels Henrik David Bohr 1922 Denmark He was awarded the Nobel Prize in physics for his in the investigation of the atom’s structure and the radiation that is sent out from them. We have more knowledge about the atom’s structure and about the radiation that is emitted from it. http://en.wikipedia.org/wiki/Niels_Bohr
Chadwick small square James Chadwick 1932 England He proved that neutrons existed. Due to the existence of neutrons, we are able to break up Uranium 235 and create atomic bombs. http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html http://www.atomicarchive.com/Bios/Chadwick.shtml