Who | What | When | Anything else useful to know |
Democritus | Said that all matter is composed of "atomos" | 4th Century BC | Founded the "Atomists" school of though, and the first (?) to propose the idea of atoms. |
John Dalton | _____'s Atomic Theory (5 laws) | 1766-1844 (lived) | Some of it has been proved false, but it is still very similar to the modern view of atoms. |
Sir J. J. Thomson | Discovered electrons, proposed "plum-pudding atom" (e.'s imbedded in pro.'s) | 1897 | Discovered using cathode ray, gases in glass tubes with discs at either end. |
Robert A. Millikan | Calculated mass of electron | 1868-1953 (lived) | Mass is 1/1840 of the mass of hydrogen |
Aristotle | Everything is composed of 4 basic elements- earth, wind, fire, water | Ancient Greece? | (blank) |
E. Goldstein | Discovered protons | 1886 | Technique similar to cathode... canal rays instead |
Ernest Rutherford | Discovered that there is a "dense, positivly charged region" | 1911 | Didn't call it a nucleus. Discovered by flinging alpha particles at gold foil, expecting them to go through. They bounced instead. |
Bohr | Said that electrons travel in concentric circular paths around the nucleus, with fixed amount of energy for each level. | (none given) | Closest to modern. Problem is that his theory only applies to Hydrogen. |
Erwin Schrodinger | Came up with a mathmatical equation for the location and energy of electrons in a Hydrogen atom | 1926 | The QMM comes from the solution to the equation. |
Dmitri Mendeleev | Arranged elements by properties and mass | 1834-1907 (lived) | (blank) |
Henry Moseley | Arranged elements by atomic number | 1913 | (blank) |
Canizaro | Developed a consistant way of finding atomic mass | (blank) | (blank) |