1. Niels Bohr Based his studies on Hydrogen Proposed energy levels
Planetary model of the Atom
We still use this today to estimate place of electron
Niels Bohr ( )
(Nobel Prize, 1922)

2. Bohr’s Model
nucleus
electron
orbit
sample-millikan1.mov

3. Bohr Analogy
An Onion
If you cut an onion in half you’ll see rings. Bohr’s model has “rings” called energy levels in which the electrons are located outside of the nucleus.

4. Bohr's Energy Levels
When an atom gains energy, electrons are raised to an excited state
fifth
fourth
Electrons move in certain allowed orbitals
third
second
Energy
Lowest Energy State is called the Ground State (n=1)
first
nucleus
Ground State is closest to the nucleus

5. Bohr to quanta
Bohr’s theory was a great accomplishment and radically changed our view of matter.
But problems existed with Bohr theory —
The theory only successful for the H atom.
So, we go on to Quantum Mechanical Model of the Atom was developed

6. Quantization of Energy was started by Max Planck
Planck’s hypothesis: Matter can only gain or lose energy in small specific amounts called a quantum.
( )

7. Louis de Broglie Proposed the wave particle duality of nature
Wave Particle duality of nature says Waves can act like particles or waves
Compared electron orbitals to waves
Related Planck’s quantum idea to electron orbitals to state that orbitals must be in WHOLE numbers.

8. Werner Heisenberg Proposed the Uncertainty Principle
Said it is impossible to know both the exact position and velocity of an electron at the same time
Make a prediction but not for sure
Einstein did not like it. He said
“God Doesn’t Play Dice”

9. Erwin Schrodinger
Used de Broglie and Planck’s work to propose a new model of the atom, in which electrons are treated as waves
Described three dimension area around nucleus called the atomic orbital to describe the probability of the electrons’ location
Electron cloud model of an atom

10. The Modern Atom Atoms have: A nucleus small, heavy part of the atom
An electron cloud
large, lightweight part of the atom
Nucleus
Electron Cloud

11. Don’t forget tonight’s homework:
Democritus – Erwin Schrodinger
Don’t forget tonight’s homework:
Update the Scientist Timeline
Draw diagrams, and list the most important discoveries that each scientist made.