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Aristotle 340 B.C.E
Aristotle described the idea of the five elements of matter. There was air (light,) earth (cool and heavy,) water (wet,) fire (hot,) and Aether, which was a devine substance that made up only the planets and stars. He believed that all mater was made up of the first four elements respectivly. Though some of his ideas useful others just veated problems in the science world.
http://atomicmodelhistory.worldpress.com/2010/11/27/aristotles-contribution -
Antoine Lavoisier 1789
Lavoisier is responsible for coming up with The Law of Conservation of Matter: matter is rearanged but never destroyed. He did this through an experiment HgO to Hg+O. Lavoisier also wrote a book called Elementary Textbook of Chemistry (1789) which was the first modern chemistry and conatined The Law of Conservation of Elements, and a list of elements that could not be broken down further. -
John Dalton 1803
John Dalton created the Atomic Theory of Matter, which stated: (1)all matter is composed of atoms (2)atoms cannot be made or destroyed (3)all atoms of the same element are identical (4) different elements have different types of atoms (5)chemical reactions occur when atoms are reaaranged (6)compounds are formed from atoms of the constiuent element. Most of these theories are still excepted today.
http://www.rsc.org/chemsoc/timeline/pages/1803.html -
Henri Becquerel 1896
Becquerel discovered radioactivity in atoms; alpha particles. With his discovery he was able to nix the idea of the invisible atom. Plus with this idea he was able to hlep Rutherford and Thomson on their idea of the atom. This also lead to the creation of nucleat meds, and weapons.
http://www.vigyanprasar.gov.in/scientists/antoinehenribecquerel,htm -
Marie and Pierie Curie 1898
The husband and wife duo of Marie and Pierie Curie used the findings of Bequerel's radioactivity to find charges in the nucleus of an atom. With this infomation they were also able to conclude that if an atom is split it will release huge amounts of energy. They also discovered the elements of radium and Polonium.
http://www.phy.pmf.unzg.hr/~dpaar/fizicari/xcurie.html -
Max Planck 1900
Max Planck came up with the formula for the Quantum Theory ; E=Nhf. E=energy, N=intiger, h=constant or Planks constant, and f=frequency. The energy emitted by a resonater could only take on certian values or quantities.
http://www.nobelprize.org/nobel_prizes/physics/lauleales/1918/plank-bio.html -
J.J. Thomson 1904
Thomson discoved the electron. He viewd the atom as something that looked like plum pudding. It was mostly positive with negative sprinkled through it. He Rutherfords teacher and influenced his work.
http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx -
Robert Milikan 1908
Robert Milikan worked on figuring out the charge of the electron. He did this through his famous Oil-Drop experiment. He found that the the charge of the electron was a single value and the same value for all forms of electricity. He built his work off of Thomson. Plus Bohr used his work to help himself later.
http://www.chemistryexplained.com/Ma-Na/Milikan-Robert.html -
Ernest Rutherford 1911
Ernest Rutherford was able to figure out that there was a central positive nucleus that was surrounded by negative orbiting electrons. There was only mass in the nucleus and everything elese was empty space. He figured this out by the Gold Foil experiment. He was also Bohr's teacher.
http://www.rsc.org/chemsoc/timeline/pages/1911.html -
Niels Bohr 1913
Niels Bohr proposed the idea of Quantum Therom through the hydrogen atom. The Quantum Theory is, energy transfered only in certian and defined quantities. Found there to be energy leveles where there electrons orbit the nucleus. the Electrons have a certian orbit but when jumping to a lower lever orbit it produces quantum light. Student of Rutherfords.
http://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-facts.html -
Henry Mosely 1913
Mosely was able to make the Periodic table more acurate by developing the application of x-ray spectra to the study of the atomic structure.He was able to come up with a closer atomic number with his work which made the table more accurate from the Mendeleev and Myeres periodic table. Plus he studied under Rutherford.
http://www.chemistry.co.nz/henry_moseley.htm -
Erwin Schrodinger 1926
Erwin was able to take Bhor's model one step further by finding an equation which could perdict where may be. This Quantum Mechanical equation model of the atom dosen't give you a direct path it just perdicts its location. The nucleus is surrounded by a dense electron cloud. Introduced sub-energy levels.
http://www.abcte.org/files/previews/chemistry/s1_p6.html -
Werner Heisenberg 1927
Hesenberg came up with the idea of Quantum Mechanics: any theory of the atom must be based on observable phenomems. He provided model for calculations the formual. This discovery helped lead to atomic bombs. He both questioned Bhor's mathmatics and worked with him. Plus he also directed the Max Planck institute in Berlin.
http://www,pbs.org/hollywoodpresents/copenhagen/story/resenrerg.html -
James Chadwick 1932
Cadwick proved the existance of neutrons. "Nuclear Electrons" in the nucleus plus protons were used to help Heisenberg's Uncertanity Principal. He was able to nix the idea of electrons in the nucleus. Plus he also worked in Rutherford's lab. These results lad to the atomic bomb and nuclear power.
http://ansnucleate.org/2011/10/19/pioneers10<1011 -
Democritus 492 B.C.E.
Democritus was in a way the start to the atom. He stated that matter could not keep being divided, there was a piece of matter that could not be divied any more. He called this "Atomos" which means, not to be cut. Atoms were small hard particles that made up all objets and were in constant motion.
http://profmokeur.ca/chemistry/history_of _the_atom.htm
