The Electron: Energy
and Waves
Objective: understand the electromagnetic
spectrum and the mathematical relationship
between energy, frequency, and wavelength
of light.
Objective: calculate the wavelength,
frequency, and energy of light using Planck’s
constant and the speed of light.
Rutherford’s Atom
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Has a small positively charged center.
Has small negatively charged particles surrounding
the nucleus.
PROBLEMS
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The negatively charged particles should be attracted to the
positively charged nucleus and move toward the nucleus;
opposite electrical charges attract.
The electrons can not be in stable orbits because they
would be constantly accelerating and that would require a
constant input of energy.
The Solution.
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The answer was found in the new field of
QUANTUM MECHANICS.
Quantum mechanics describes the wave –
particle duality of the electron
Electrons behave like particles of matter.
But they also behave like forms of energy.
Quantum mechanics describes the electron
in terms of energy and matter.
Energy
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Energy is transmitted in the form of waves.
Properties of waves.
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Frequency = the number of waves that pass a
certain point in one second. (measured in hertz)
Wavelength = the distance from one crest to
another. (measured in meters)
Amplitude = the height form the rest position to
the highest point. (measured in meters)
Velocity = the speed of the wave. (measured in
meters per second; m/s)
Typical Waves
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wavelength x frequency = velocity
λ . ν = velocity
meters . 1/seconds = meters / second
If wave is an electromagnetic wave the velocity of the wave is
equal to the speed of light. (c = 3.00 x 108 m/s)
Electromagnetic waves.
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The motion of electrons is described in terms of light energy.
Light travels in the form of waves; light also behaves as a
particle.
Light energy and electron energy are emitted in “packets of
energy” called PHOTONS.
Visible light is one form of the electromagnetic spectrum.
Wave Calculations
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What is the velocity of a wave that has a wavelength of
2.5 meters and a frequency of 3.5 hertz?
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What is the frequency of green light that has a
wavelength of 490. nanometers? (1 nm = 10-9 m)
Wave Calculations
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A popular radio station broadcast with a
frequency of 94.7 megahertz. What is the
wavelength of the broadcast? (1 Mhz = 106 hz)
Photon
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A photon is a particle of electromagnetic radiation with
no mass that carries a quantum of energy.
Ephoton = hν
h is called Planck’s constant (6.626 x 10-34 J.s)
What is the energy of a photon of green light?
The higher the frequency the more energy an
electromagnetic wave contains.
Electron configurations
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Because each element has a unique electron configuration each
element gives off a different amount of light energy. (photons)
Each element can be identified by the light it gives off.
These are called bright line spectrums.
Calculations
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Page 147 of text:
problem 65 – 76
SHOW ALL WORK:
WHAT
HOW
DO IT
ANSWER (round to correct significant digits)