WaveParticle Duality JJ Thomson won the Nobel prize for describing the electron as a particle His son George Thomson won the Nobel prize for describing the wavelike nature of the electron The electron is a particle ID: 441449
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Slide1
Energy and ElectronsSlide2
Wave-Particle Duality
JJ Thomson won the Nobel prize for describing the electron as a particle.
His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron.
The electron is a particle!
The electron is an energy wave!Slide3
Confused??? You’ve Got Company!
“No familiar conceptions can be woven around the electron; something unknown is doing we don’t know what.”
Physicist Sir Arthur
Eddington
The Nature of the Physical World
1934Slide4
The Wave-like Electron
Louis
deBroglie
The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves.Slide5
c =
C
= speed of light, a constant (3.00 x 108 m/s)
= frequency, in units of hertz (hz, sec-1)
= wavelength, in meters
Electromagnetic radiation propagates through space as a wave moving at the speed of light.Slide6
Types of electromagnetic radiation
:Slide7
Electromagnetic Radiation (Light) as a Key to Understanding Electron Paths
Early scientists discovered that Electromagnetic radiation (light) is given off by atoms of an element when they have been excited by some form of energy
Furthermore, atoms of different elements give off different colors of light when they are excited
.Slide8
When salts containing Li, Cu, and Na dissolved in methyl alcohol are set on fire, brilliant colors result.
Li
Cu
NaSlide9
Spectral Analysis of Emitted Light from Excited AtomsWhen the emitted light from excited atoms was passed through a prism, a curious spectrum of discrete lines of separate colors, separate energies, was observed rather than a continuous spectrum of
ROY G BIV
.Furthermore, different elements show totally different line spectra.In fact, line spectra are used to identify the presence of different elementsSlide10Slide11
Interpretation of Atomic Spectra
The line spectrum must be related to energy transitions in the atom.
Absorption = atom gaining energy
Emission = atom releasing energy
Since all samples of an element give the exact same pattern of lines, every atom of that element must have only certain, identical energy statesThe energy of an atom is quantized – limited to discrete values
If the atom could have all possible energies, then the result would be a continuous spectrum instead of linesSlide12
Continuous Spectrum
Atomic Line Spectrum
NaSlide13
E = h
E
= Energy, in units of Joules (kg·m
2
/s2
)
h
= Planck’s constant (6.626 x 10-34 J·s)
= frequency, in units of hertz (
hz
, sec
-1
)
Max Planck
, a German Physicist, studied the emission of light by hot objects. He determined that there is a minimum amount of energy lost or gained by an atom, called a
quantum
of energy.
Energy EquationSlide14
Long
Wavelength
=
Low Frequency
= Low ENERGY
Short
Wavelength
= High Frequency =
High ENERGY
Wavelength TableSlide15
Calculating EnergyWhat is the energy of a photon of microwave radiation with a frequency of 3.20 x 1011 s-1 ?E = h
h = 6.626 x 10-34 J x s
= 3.20 x 1011 s-1
E = (6.626 x 10-34 J x s)(3.20 x 1011
s-1)
E = 2.12 x 10-22 JSlide16
Calculating frequencyOrange light has a wavelength of 6.20 x 10-7 m. What is the frequency?
c
= speed of light = 3.00 x 10
8
m/s
3.0 x 10
8
m/s
6.2 x 10
-7
m
= 4.8
x 10
14
s
-1
=
Slide17
Relating Frequency, Wavelength and Energy
Common re-arrangements: