| Term | Definition |
|---|
| Democritus | stated that atoms are indivisible; used greek root word 'atomos'; thought atoms were made of single material formed into different shapes and sizes |
| Dalton | four major points of his theory; stated that you could never have a particle that is indivisible, atoms of the same substance are the same, atoms of different elements are different, and atoms join together to create compounds or new substances |
| Thompson | conducted cathode-ray tube experiment by sending negatively charge particles toward a positively charged plate; concluded that there were negatively charge particles in the atom, but there must also be positive one because otherwise the negative particles would repel each other; made the plum pudding model |
| Rutherford | aimed positively charge particles at a thin piece of gold foil and watched as some bounced back, and others went all over the place; changed atomic theory so now it stated that a dense, positively charged nucleus and the negatively charge electrons surround the nucleus |
| Bohr | improved on his colleague's theory by changing the location of electrons so that they now stayed on strict orbits, yet they could switch levels but never go in between, the nucleus still stays in the middle |
| Modern Atomic Theory | worked on by Schrodinger and Heisenberg; positively charged nucleus surrounded by electron clouds--the probable location of electrons, but the exact location of an electron is not able to be predicted |
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