1. 5.3 Physics and the Quantum Mechanical Model
QMM grew out of a study of light
1666 Newton said light consists of particles

2. Light
By 1900, there’s enough experimental evidence to convince scientists that light consists of waves

3. Wavelength (λ, Greek symbol Lambda)
Measured in m or nm
Frequency (ν, Greek symbol nu)
# waves per unit of time
Measured in cycles per second
SI unit = hertz (Hz)
Reciprocal second, s-1 (1/s)
Amplitude = height from zero to crest

4. C = νλ
Frequency and wavelength are inversely proportional to each other
All electromagnetic waves travel in a vacuum at a speed of c = x 108 m/s

5. Calculate the wavelength of the yellow light emitted by sodium lamp if the frequency of the radiation is 5 x 1014 Hz.

6. Electromagnetic Spectrum

7. Electromagnetic Spectrum
Wave model  light is made up of electromagnetic waves
Visible light ranges from
red (low energy, 700 nm) to
violet (high energy, 380 nm)

8. Atomic Spectra Atoms absorb energy, e- move to higher energy levels.
e- lose energy by giving off light as they return to lower energy levels
Light emitted by atoms is a mixture of specific frequencies, each frequency corresponds to a certain color
Emission spectrum

9. Emission spectrum of an element is like a fingerprint, no two elements have the same
Used to identify elements

10. Lowest possible energy of electron is its Ground State
Absorbs energy and moves to EXCITED STATE
Quantum of energy (light) emitted when electron drops back to lower energy level
Emission takes place in an abrupt step called electronic transition

11. > Frequency >Energy
Energy and Frequency
Photon - A quantum of light (packet of energy)
The light emitted has a frequency directly proportional to energy change of electron
> Frequency >Energy

12. Energy per photon ∆E = hc/λ ∆E = hν h = 6.626 x 10-34 J ∙ s/photon
(h = Planck’s constant)

13. Hydrogen Spectrum

14. Lyman series- transition to n = 1
(ultraviolet)
Balmer series- transition to n = 2
(visible)
Paschen series- transition to n = 3
(infrared)

15. Quantum Mechanics
De Broglie predicted that all moving objects have wavelike behavior
Classical mechanics describes the motions of bodies much larger than atoms
Quantum mechanics describes the motions of subatomic particles and atoms as waves

16. Heisenberg uncertainty principle-it is impossible to know exactly both the velocity and the position
of a particle at
the same time