1. Modern Atomic Theory

2. Bohr Model (1913)
All materials are made up of tiny solid particles called atoms.
At the center of this atom is a dense positive area consisting of protons and neutrons called the nucleus.
Electrons move in definite orbits around the nucleus.
These orbits or energy levels are located at certain distances from the nucleus.

3. Bohr’s Model
nucleus
Electrons

4. Neils Bohr

5. This isn’t the current model
Bohr himself quickly disagreed with his own model.
The problem is with the orbits of the electrons.

6. Wave Model (present day)
based on complex math equations
orbits are more complex than originally thought
de Broglie stated that electrons (particles) have wave properties, and he viewed these as standing waves, like those produced when a guitar string is plucked (classical physics.)
Schrodinger assumed that the electron in Hydrogen behaves as a standing wave.

7. Wave Model (continued)
When Schrodinger’s equation is analyzed, many solutions are found.
Each solution represents an atomic orbital.
An atomic orbital is the most probable location for finding an electron.

8. What is an orbital?
It is not a Bohr orbit (not moving in a circular path.)
How is the electron moving?
We don’t know!
There is a fundamental limitation to just how precisely we can know both the position and momentum of a particle at a given time

9. This is kind of how we assume an electron travels

10. Heisenberg Uncertainty Principle
The more accurately we know the particle’s position, the less accurately we can know it momentum and vice versa.
We can’t know the exact motion of the electron around the nucleus.
The area that an electron orbits is called an “electron cloud”

11. Louis de Broglie Erwin Schrodinger

12. Werner Heisenberg

13. Homework Read section 5.1, 5.4 and 5.5 Do questions on pages 175-177
1-4, 12-18