1. Objectives
To understand how the emission spectrum of hydrogen demonstrates the quantized nature of energy
To learn about Bohr’s model of the hydrogen atom
To understand how the electron’s position is represented in the wave mechanical model

2. A. The Energy Levels of Hydrogen
Only certain types of photons are produced when excited Hydrogen atoms release energy. Why?

3. A. The Energy Levels of Hydrogen
Atomic states
Excited state – atom with excess energy
Ground state – atom in the lowest possible state
When an H atom absorbs energy from an outside source it enters an excited state.

4. A. The Energy Levels of Hydrogen
Energy level diagram
Energy in the photon corresponds to the energy used by the atom to get to the excited state.

5. A. The Energy Levels of Hydrogen
Only certain types of photons are produced when H atoms release energy. Why?

6. A. The Energy Levels of Hydrogen
Quantized Energy Levels
Since only certain energy changes occur the H atom must contain discrete energy levels.

7. B. The Niels Bohr Model of the Atom (1913-1915)
Bohr’s model of the atom
Quantized energy levels
Electron moves in a circular orbit
Electrons jump between levels by absorbing or emitting photons of a particular wavelength
Able to mathematically explain the emission spectrum of Hydrogen (compare with Rutherford)

8. “Curiouser and curiouser” said Alice

9. B. The Bohr Model of the Atom
Bohr’s model of the atom was not totally correct.
Had difficulties with spectra of larger atoms
Electrons do not move in a circular orbit and don’t seem to behave like discrete particles all the time
Maybe small particles, such as electrons, can also behave like waves having a dual nature (just like photons)……?

10. C. The Wave Mechanical Model of the Atom (de Broglie and Schroedinger – mid-1920’s)
Orbitals
Nothing like orbits
Probability of finding the electron within a certain space