1. Physics and the Quantum Model

2. Light
The idea for the the quantum mechanical model grew out of the study of light
Light consists of waves
The amplitude of a a wave is the height from zero to crest
Wavelength (λ) is the distance between crests
Frequency (ν) is the number of wave cycles that pass a given point per unit of time
Frequency is measured
in hertz (Hz)

3. Light
c= λν
c is a constant, equal to x 108 m/s, so frequency and wavelength are inversly proportional

5. Atomic Spectra
Atoms can absorb energy that raises electrons into higher energy levels.
The electrons then lose the energy by emitting light when electrons return to their lower energy level.
The light emitted by electrons only contains certain wavelengths of light.
Each frequency corresponds to a specific color
Each element emits a unique atomic emission spectrum

6. Uses of Atomic Spectra

7. How it Works
An electron has a lowest possible energy called it’s ground state.
For hydrogen, its ground state is n=1
Absorbing energy can excite the electron to n=2,3,4,5 or 6
A quantum of energy in the form of light is emitted when an electron drops back to a lower energy level
The light emitted by an electron transition from higher to lower is derectly proportional to the energy change in the electron, therefore each transition produces a line of a specific frequency in the spectrum

9. Quantum Mechanics Light has a dual wave/particle nature
Particles of light are called photons
Experiments showed that electrons also behaved like particles and waves
This wave like nature is used in electron microscopes since electrons have a much smaller wavelength than visible light
Quantum mechanics describes the motion of subatomic particles and atoms as waves

10. Heisenburg Uncertainty Principle
It is impossible to know exactly both the velocity and position of a particle at the same time

11. Tying it Together
The discovery of matter waves paved the way for Schrodinger’s quantum mechanical atom model. His theories include the wavelike motion of matter and the uncertainty principle.