Transcript Light and the electron

Light and the electron
Quest continues to discover the
structure of atom and how electrons
are arranged within atoms.
Wave Nature of Light
► Electromagnetic
radiation – form of energy
exhibiting wave-like behavior
► Ex. Visible light
Wavelength (λ)
► Distance
between adjacent peaks in a wave.
Measured in meters.
Speed of light (c)
► Light
travels at 186,000 mi/s
►
3.0 x 108 m/s
► c = 3.00 x 108 m/s
Frequency (Ʋ)
► Number
of peaks which pass a point per
second.
► Ʋ = 1/s (Hz)
Wavelength vs. Frequency
Putting it together
►c
= λƲ
► 3.00 x 108 m/s = λƲ
► Pg. 121 practice problems 1-4
Electromagetic radiation (light)
To microwave
Particle Nature of Light
► Wave
nature of light didn’t explain many
important aspects – Why heated objects
emit only certain frequencies of light at
given temp.?
► Quantum concept – heated objects emitting
different frequencies of light. Energy
emitted corresponds to certain Ʋ & λ
► Quantum- minimum amount of energy that
can be gained or lost by an atom
Max Planck
► Energy
of quantum is related to the frequency of
the emitted radiation
► Equantum = hƲ
► E = energy
►Ʋ = ?
► h (Planck’s constant) = 6.626 x 10–34 J · s
► c = λƲ
► Greater the frequency, greater the energy –
directly proportional
Albert Einstein
► Proposed
that electromagnetic radiation has
both wavelike and particle-like natures.
► Extended upon Planck’s equation –
photoelectric effect
► Pg. 124 practice problems 5,6
Photoelectric effect
Light of a certain frequency shines on
an object, electrons are ejected from
the surface.
Atomic Emission Spectra – light
produced in glowing neon signs
► Pass
energy through tube filled with gas
► Causes electrons to absorb energy & become
excited
► As unstable, excited electrons lose energy and
spiral towards the nucleus they give off energy
that corresponds with certain frequencies of light
► When emitted light is passed through a prism→
atomic emission spectra
► Each atom’s atomic emission spectrum is unique
and can be used to determine if that element is
part of an unknown compound. Pg. 126
Bohr
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Bohr
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Bohr
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Bohr
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Bohr
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Hydrogen spectrum