| A | B |
|---|
| smallest pieces | everything made of smallest pieces called atoms |
| hard spheres | atoms are small, solid spheres |
| plum pudding | positive mass with negative particles throughout |
| nuclear model | positive charge located in center surrounded by negative charges |
| planetary model | electrons travel around the nucleus in energy levels |
| quantum model | electrons located in 3-D cloud surrounding nucleus |
| Democritus | named the atom |
| Schrodinger & Heisenberg | mathematics to determine probability of electrons' locations |
