1. Arrangement of Electrons in Atoms
The Development of a New Atomic Model - 4.1

2. The Old Atomic Model
Problem with Rutherford model – no explanation of where e-s are
New info about light led to new model of the atom
Before 1900 scientists thought light traveled like a wave.
We know now that light behaves like a wave and like a particle

3. The Wave Description
Called the dual wave-particle nature of light!
Electromagnetic Radiation - form of E that exhibits wavelike behavior as it travels thru space
Electromagnetic Spectrum - all of the forms of electromagnetic radiation (visible light, x-rays, uv and infrared light, micro and radio waves)

4. The Wave Description
All types of emag rad. move at 3.00 x 108 m/s in a vacuum. (slightly slower thru matter)
This is the speed of light

5. The Electromagnetic Spectrum

6. Wavelength and Frequency
Wavelength - λ the distance between corresponding pts on adjacent waves
Frequency - ν the number of waves that pass agiven point in a specific time, usually 1 second
Frequency is expressed in Hertz (Hz)

7. The Relationship B/T Freq. and Wavelength
c = λν
The speed of light = wavelength times frequency
The wavelength of red light is 7.6 x 10-7 m, calculate the frequency.
F = speed      =  x 108 m/s wavelength            7.6 x 10-7 m
Frequency = 3.9 x 1014Hz

8. The Photo-electric Effect
The emission of e-s from a metal when light shines on the metal
Light had to be a certain freq. to emit e-s

9. The Particle Description of Light
Planck proposed idea of quanta (E packets)
Quantum of energy - the minimum quantity of E that can be lost or gained by an atom

10. The Particle Description of Light
E = hν
Where E is the energy in joules of a quantum of radiation
υ is the frequency in s-1
h is Planck's constant of x J *  s

11. Einstein and the dual particle-wave nature
Ein. supported Planck by proposing the duality of light as particle and wave
Ein. proposed particles of light carry a quantum of E called photons (0 mass)

12. Einstein and the dual particle-wave nature
The E of a photon depends on the υ of rad.
E absorbed in whole # of photons
Different metals need diff. υ to remove an e-

13. The Line Emission Spectrum
LES = the result from a narrow beam of the emitted light that is shined through a prism when it separated into colors of the visible spectrum
The Continuous Spectrum

14. The H atom and the LES
Electric current passed thru a gas at a low pressure

15. E Levels
Ground state - the lowest E level of an atom (very stable level)
Excited state - a state in which an atom has a higher potential E than it has in its ground state

16. E Levels
When an e- falls from the excited state, a photon is given off - the E of the photon is = to the E difference
H only emits certain freq. so e- exists in specific E levels