| A | B |
|---|
| Believed that atoms were indivisible (no evidence) | Democritus |
| Believed that atoms were indivisible (evidence) | John Dalton |
| Atoms of the same element are identical | John Dalton |
| atoms of one element are different from another element | John Dalton |
| atoms combine in simple whole # ratios to form compounds | John Dalton |
| atoms separate, join, and rearrange in a chemical reaction | John Dalton |
| discovered the electron | J. J. Thomson |
| performed the cathode ray experiment | J. J. Thomson |
| determined the charge and mass of an electron | Robert Millikan |
| performed the oil drop experiment | Robert Millikan |
| the atom is mostly empty space with a dense, positively charged center | Ernest Rutherford |
| performed the gold foil experiment | Ernest Rutherford |
| developed the plum pudding model | J. J. Thomson |
| electrons move in circular orbits at fixed distances from the nucleus | Niels Bohr |
| moving electrons have wave like properties | Louis de Broglie |
| developed a mathematical model to describe the motion of electrons | Erwin Schrodinger |
| confirms the existence of neutrons | James Chadwick |
| current atomic model | quantum mechanical model |
