Bohr Model And Aes
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Bohr Model And Aes

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Bohr Model And Aes Bohr Model And Aes Presentation Transcript

  • How does this work? (Neon Signs)
  • What do we know about neon signs?
    • Electricity is passed through tube full of neon gas
    • Neon atoms in tube absorb this energy
      • What happens when something absorbs energy?
    • Neon atoms in tube become excited
      • Stable of Unstable?
      • What happens when something is unstable?
      • What do we see released energy as?
        • Electromagnetic radiation…visible light!!!
  • EM spectrum
    • What happens when we pass sunlight through a prism?
      • Continuous spectrum of colors
      • ROYGBIV
  • What happens when we pass light from neon gas or hydrogen gas through prism?
    • Separation of colors
    • Discontinuous spectrum
    • This is called…
  • ATOMIC EMISSION SPECTRUM (AES)
    • AES of an element is the set of frequencies of the electromagnetic radiation emitted by the atoms of that element
    • Individual lines of color
    • Only certain lines of color appear for certain elements…
      • What does this mean…????
    • Every element has a unique AES
    • Why is this important?
  •  
  •  
  • Hydrogen Atom
    • Why did scientists want to use hydrogen?
      • How many protons?
      • How many electrons?
      • Do you think it is easy to use?
      • Check out the AES of hydrogen gas…
  •  
  • Neils Bohr (1913)
    • Danish Physicist
    • Worked with Rutherford
    • Quantum Model of Hydrogen atom
      • Predicted lines of Hydrogen AES
    • Hydrogen has only one electron but why do we get different colored lines on AES???
      • We get hydrogen atoms excited…
      • Electrons move to excited levels
    • H has certain allowable energy states….
      • The lowest energy state is called the GROUND STATE
  • Bohr’s Hydrogen Orbits…
    • He related H’s energy states to the motion of an electron in an atom
    • Single electron in moves around nucleus in circular orbits
    • Smaller orbit, smaller radius, closer to nucleus means…?
      • Lower energy level
    • Larger orbit, larger radius, farther from the nucleus means…?
      • Higher energy level
  •  
  • Bohr’s Quantum Model
    • Assigned quantum numbers, n, to each orbit
    • Calculated orbits radius
      • Chart on page 127
    • 1 st orbit  n=1 (first energy level)
    • 2 nd orbit  n=2 (second energy level)
    • 3 rd orbit  n=3 (third energy level)
  •  
  •  
  • When we add energy, what happens to electron?
    • Electron excited
    • Moves to next energy level
    • Excited=?
      • unstable
    • What happens when something is unstable?
      • Wants to get back to being stable
      • Releases energy
      • Goes back down to lower energy level
    • Photon is emitted corresponding to the 2 different energy levels associated with the 2 orbits
  •  
  • NEW EQUATION
    • /_ E= E higher e- orbit - E lower e- orbit =E photon =hv
    • Only certain energies are possible so only certain frequencies, v, of EM radiation are emitted
    • Lets look at the AES of Hydrogen…
    • How many lines are there?
    • So how many different types of radiations are we seeing?
    • There are 4 electron transitions account for lines in the hydrogen spectrum
    • Going from 3 rd orbital to 2 nd orbital…
    • Going from 4 th orbital to 2 nd orbital…
    • Going from 5 th orbital to 2 nd orbital…
    • Going from 6 th orbital to 2 nd orbital…
  • Names for these lines…
    • Balmer Series
      • The 4 visible color lines
      • Electrons that drop into n=2
    • Other electrons transitions not visible
      • Lyman series
        • Ultraviolet light
        • Electrons drop into n=1
      • Paschen series
        • Infrared
        • Electrons drop into n=3
  •  
  • Problems with Bohr’s Model
    • Predicted AES lines of H but not any other elements
    • Did not account for all chemical behavior
    • Big problem…
      • Electrons don’t move in circular orbits
      • Time for a new model…