The History of the Atomic Model

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
Thompsons Model (1904)

• Discovered electrons
• Suggested electrons are embedded in positive mass
• Raisins in Plum Pudding Model
• No neutrons

5
Rutherfords Model (1911)

• Introduced nucleus
• No neutrons
• Electrons orbit nucleus like planets around a sun

6
Bohrs 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 electrons 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?

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