1. The History of the Atomic Model Journey into the Unseen

2. Aristotle (384-322 BC) Greek philosopher Hypothesized that all things in nature are composed of four elements Fire, Air, Earth, Water

3. Democritus (460-370 BC) Greek philosopher First suggested all things in nature can be divided into atoms Suggested atoms were solid, indivisible particles

4. Thompson’s Model (1904) Discovered electrons Suggested electrons are embedded in positive mass “Raisins in Plum Pudding Model” No neutrons

5. Rutherford’s Model (1911) Introduced nucleus No neutrons Electrons orbit nucleus like planets around a sun

6. Bohr’s Model (1922) Electrons orbit the nucleus at different levels of energy Neutrons discovered in 1932 by James Chadwick

7. Standard Model Based on work of physicists Heisenberg and Schrodinger Atoms are 99.9% empty space An electron’s actual position can never be known, so there is only a probability of where it will be Electron orbits thought of as a cloud

8. Model of the Future Matter and Antimatter? Quarks and Leptons? What do you predict?