Atomic Theory Timeline Kyle, Justin, Mike
- 1. Democritus Abdera 460-370 B.C. He first attempted to create materialism. Everything is composed of atoms .
- 2. Antione Lavoisier 1772 Total mass of a product of a chemical reaction is always the same thing as the total mass Conservation of mass
- 3. Law of Conservation of Mass 1789 Matter can not disappear it can only be rearranged At high speeds mass changes to energy
- 4. Joseph Louis Proust 1798 Created the law of constant composition Constant composition
- 5. Dalton’s Atomic Theory 1799 Law of constant composition Oxygen and Carbon combined make 2 compounds
- 6. John Dalton 1803 Recorded the first tables of relative atomic mass Atomic number
- 7. Law of Definite Proportions 1805 Law say if formula AB is constant then the weight ratio will stay the same Weight ratio stays the same
- 8. Dmitri Mendeleev 1869 Created the periodic table List of elements
- 9. Eugene Goldstein 1886 Investigated X-rays Discovered cathode rays
- 10. Erwin Schrodinger 1887-1961 Created the Schrodinger Wave Equation Used to describe behavior of electrons in atoms
- 11. Cathode Ray Tube 1893 2 positive leads connected into a neon tube will make it light up Electric makes light
- 12. J.J. Thompson 1897 Discovered that cathode rays are small steams of atoms An electron has a negative charge
- 13. Plum Pudding Atomic Model 1897 He said that there has to be a positive and negative charge to balance out an atom Atoms are neutral
- 14. Ernest Rutherford 1898 Discovered and studied alpha particles and discovered the nucleus Nucleus
- 15. Marie Curie 1902 Discovered the radio active elements Radio active elements
- 16. Rutherford Model 1909 Model of a nucleus and electrons Nucleus is in the center and the electrons orbit it
- 17. Robert Millikan 1911 Made an oil drop experiment Made electron have an electric charge
- 18. Bohr Planetary Model 1913 He thought that electrons only orbit in one direction They are called stationary orbits
- 19. Niels Bohr 1913 Considered the term of stationary orbits for the electrons and that there is more than one level of orbit Electron cloud
- 20. Henry Mosdeley 1913 Numbered the elements Order of elements
- 21. Quantum Mechanical Model Mathematical equation developed by Schrodinger Calculated where electrons are at any given moment
- 22. Gold Foil Experiment 1920 It showed that the nucleus is positive and the electrons orbit it
- 23. James Chadwick 1932 Found the neutron His discovery led to nuclear fission and the atomic bomb
- 24. Lise Meitner 1966 First discovered nuclear fission