Emission Spectrum Animation

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Emission Spectrum Animation
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Light and Energy

• The electromagnetic spectrum (p. 335)
• Particles (photons) and waves at the same time!
• c f?
• The greater f (frequency), the smaller ?
  (wavelength)
• The greater f, the higher the energy of the EM
  radiation.

Energy hf h is Planks Constant
6.6262x10-34Js
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Energy and Frequency

• The higher the frequency, the greater the energy

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Which has higher energy red or blue light?
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• Emission spectra known for hundreds of years
• Niels Bohr suggests a reason energy levels
• Electrons orbiting in shells around the nucleus
• Energy levels differ from one another

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Electrons and Light

• When an atom absorbs energy, electrons are
  promoted to higher energy levels.
• When the atom releases the absorbed energy, the
  electron falls back down to lower energy levels
  and EM radiation is given off (sometimes light)

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There are only certain posibilities

• Electrons can only exist at discrete energy
  levels
• Therefore, in changing levels, only certain
  amounts of energy can be released
• These amounts are unique to every element
• Page 343 in book illustrates

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A Demo

• http//www.visionlearning.com/library/flash_viewer
  .php?oid1347mid51
• http//jersey.uoregon.edu/vlab/elements/Elements.h
  tml

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(No Transcript)
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SPECTRUM ACTIVITY
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How are the lines of the line spectrum formed?
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Spectrum
Excited State
n4
UV
Excited State
n3
Excited State unstable and drops back down
Vi s ible
Excited State
But only as far as n 2 this time
n2

• Energy released as a photon

• Frequency proportional to energy drop

IR
n1
Ground State
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Summary

• Electron normally in Ground State
• Energy supplied as heat or electricity
• Electron jumps to higher energy level
• Now in Excited State
• Unstable
• Drops back to a lower level

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• Energy that was absorbed to make the jump up is
  now released as a photon
• Frequency depends on difference in energy levels
  E2 - E1 hf h is Planks Constant and f is
  frequency of light
• When electron falls to
• n 1 level gives UV Range
• n 2 level gives Visible Range
• n 3,4 or 5 levels gives IR Range