| A | B |
|---|
| J.J. Thomson | studying cathode rays-led to finding that atom can be broken into smaller parts-found electron |
| Democritis | 1st atomic theory-no scientific evidence-named atom (atomos) |
| John Dalton | atoms=tiny hard spheres, created atomic theory, element atoms all alike and formed compounds, law of definite proportions |
| Mendeleev | created 1st periodic table based on elemental properties (organizes periodic table) |
| W. Ramsay and M. Traves | found Krypton, Neon, and Xenon within 3 months of using periodic table |
| Einstein | 1st real proof atoms existed, calculations of Brownian Motion heat as atomic motion and momentum conservation |
| Ernest Rutherford | found atom mostly empty space, has dense center, and identified proton |
| Niels Bohr | electrons in an atom move in a set path around nucleus, similar to planets around sun-electrons orbit nucleus in fixed orbits, fixed energy |
| James Chadwick | focused on radio activity, with Rutherford knew there had to be another particle with the proton in nucleus (missing mass)- neutron |
| Mueller | 1st to see atom with ion microscope |
