| A | B |
|---|
| Rutherford | Gold Foil Exeperiment, An atom is mostly empty space with a dense positively charged region he called the nucleus. |
| J.J. Thomsen | Cathode ray tube experiment discovered the electron. His model was called the plum pudding model |
| Bohr | Electrons exist outside the nucleus in definite orbits he called energy levels |
| Schrodinger | Developed the quantum theory model which said electrons are found in regions of probability called orbitals |
| Dalton | Developed a 5 part atomic theory. He thought as atoms indivisible balls which combine in multiple proportions with whole number ratios. |
| Democritis | Atoms are indivisible invisible balls of matter |
| Hund's rule | before pairing, single electrons occupy orbitals of equal energy with parallel spins until all orbitals of equal energy have one electron |
| Aufbau principle | electrons fill lower energy levels first |
| Pauli exclusion principle | each orbital can hold a maximum of two electrons with opposite spins. |
| Ground state | When electrons are in their lowest energy states |
