history of chemistry By bjfelker 300 (BC) Aristotle states the four elements-earth, wind, fire, water http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html 430 (BC) Democritus states atoms to be the simplest form of matter and all matter was made of them http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html Jan 1, 1802 John Dalton states atomic theory-all matter is made of small invisible atoms http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html Jan 1, 1855 Eugene Goldstein discoveres the proton http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html Jan 1, 1897 thomson discovers the electron and states that the electron is the only part of an atom http://www.aip.org/history/electron/jjhome.htm Jan 1, 1908 Rutherford found the the first half-life of an element, thought the atom was syrrounded by nearly weightless electrons http://www.pbs.org/wgbh/aso/databank/entries/bpbohr.html -http://galileo.phys.virginia.edu/classes/252/Rutherford_Scattering/Rutherford_Scattering.html Jan 1, 1909 Robert Millikan discovers the weight of an electron using charged oil drops http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html Jan 1, 1922 Niels Bohr makes model of atom with electrons based on different energy levels outside of the nucleus http://www.pbs.org/wgbh/aso/databank/entries/bpbohr.html Jan 1, 1932 James Chadwick discovers the neutron http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html
