1. Atomic Theory

2. Let’s Take a Trip Through Time!

3. Democritus 400 B.C.
There are various basic elements from which all matter is made
Everything is composed of small atoms
Some atoms are round, pointy, oily, have hooks, etc. to account for their properties

4. Democritus’s Model

5. John Dalton Introduced his ideas in 1803
Each element is composed of extremely small particles called atoms
All the atoms of a given element are identical, but they differ from those of any other element
Atoms are neither created nor destroyed in any chemical reaction

6. Dalton’s Model

7. J.J. Thompson 1904
Discovered electron (negative particle) in the Cathode Ray Experiment
Plum Pudding model 1904
Electrons in a soup of protons (positive charges)
There is an equal number of positive and negative charges because the atom is neutral

8. Cathode Ray Tube Experiment

9. Thompson’s Model
Protons
Electrons

10. Ernest Rutherford 1910 Nucleus Theory 1910
alpha particle gold foil experiment
An atom’s mass is mostly in the nucleus
The nucleus has a positive charge because it contains the protons and because it is so large in mass it contains another particle called the neutrons(neutral)
Electrons in fixed orbit

11. Alpha Particle Experiment

12. Rutherford Model

13. Niels Bohr 1913 Planetary Model 1913
Nucleus surrounded by orbiting electrons at different energy levels
Electrons have definite orbits
Worked on the Manhattan Project (US atomic bomb)

14. Bohr’s Model Neutrons (No charge) Electrons (negative charge)
Protons (positive charge)

15. Ernst Schrödinger Werner Heisenberg Quantum Mechanical Model 1926
Electrons are in probability zones called “orbitals”, not orbits and the location cannot be pinpointed and they are constantly moving (they are not moving in circular orbits)
Schrödinger and Heisenburg’s Model of the Atom is the Model still accepted today.

16. Schrödinger and Heisenburg’s Model of the Atom