1. Bohr Model vs. Quantum Theory

2. Wave/Particle Paradox
Light sometimes acts as a particle and sometimes acts as a wave.
Thomas Young noticed that when electrons are forced through a narrow slit, a pattern of wave interference emerged.
He was familiar with Rutherford’s Thompson’s experiment that showed electrons are particles and needed to reconcile the two points of view.

3. Double Slit Experiment
What it would look like if a wave went through two slits….
What it would look like if particles go through two slits….
What it looks like when electrons go through two slits…

4. Wave/Particle Paradox
This reconciliation led to the development of the Quantum Mechanical Model of the atom.
The Quantum Mechanical Model is based on complex mathematical equations developed by Erwin Schrodinger that describe the wave nature of the atom and the locations of the electrons.

5. These are the equations that determine where electrons can “live”
(credit to Jack Helgeson for
writing the equations for
Ms. LaPlante years ago)

6. Bohr (left side of table)
Nuclear model (model says atoms have a nucleus)
Electrons orbit the nucleus like planets around the sun.
Electrons are treated like particles.
Electrons’ energy is quantized.

7. Quantum Theory (right side of table)
Nuclear model
Electrons occupy orbitals, which are probability spaces described by mathematical models.
Electrons are treated like waves.
Electrons’ energy is quantized.

8. When atom is not energized
Bohr Model
When atom is not energized
When atom is energized

9. When atom is not energized
Quantum Model
When atom is not energized
When atom is energized

10. Some more pictures of orbitals (from the website http://winter. group

11. Quantum Theory (based partly on Heisenberg’s Uncertainty Principle)
The position and the momentum of a moving object cannot simultaneously be measured and known exactly
There is an inherent limitation to knowing both where a particle is at a particular moment and how it is moving in order to predict where it will be in the future

12. Quantum Theory
An electron is in an orbital – probability space where an electron can be found a certain percentage of the time as defined by Shrodinger’s equations
An orbital can hold 2 electrons (this means the bigger the energy level, the more orbitals it has)
(add this to your notes): s = 1 orbital, p = 3 orbitals, d = 5 orbitals, f = 7 orbitals