The Development of a New Atomic Model

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					The Development of a New Atomic
            Model
• What prevents the electron from being
  drawn into the nucleus?
• The study of the absorption and emission
  of light, through light upon the subject
The Electromagnetic spectrum
  Electromagnetic energy is a strange self-propagating combination
             of electricity and magnetism without mass.
               Electromagnetic radiation comes in a
  continuous spectrum of frequencies, wavelengths, and energies.
Wavelength
• The distance of one complete wave
• Expressed in meters per wave
• λ= meter/wave
Frequency
• The number of waves that pass a given
  point in a specific time
• Expressed in waves per second
• V = waves/second
• =Hertz
Frequency*wavelength=speed
• The velocity of a wave, C, is related to the
  wavelength and frequency of the wave
• C=λv meter/sec=meters/wave *
  waves/sec
• For waves on an ocean this is the speed of
  the wave through the ocean
• For sound waves, the speed of sound
• For light, the speed of light
 The Photoelectric effect
     Refers to the emission of
electrons from a metal when light
        shine on the metal
Light as Particles
• Max Planck proposed that light is not a
    continuous wave but comes in packets called
    quanta
• Quanta of light have different energies as do
    moving particles
•   Planck and Einstein determined that the energy
    of a photon (wave-packet)= Planck's constant *
    frequency of the wave
                      • E=hv
• Higher frequency light has more energy
The particle theory of light explains
     the photoelectric effect
    How do solar cells work?
Line Spectra
• A spectrum that only contains certain
  colors , or wavelengths
• Produced by electrons “jumping” between
  electron orbitals
  Bohr model
The Bohr Model
Line spectra explained
Bohr Model demolished
• The Bohr model works great for
  hydrogen
• It fails in explaining the spectral lines
  of helium or any other element with
  more than one electron
• Oh well, back to the drawing board
   –Now known as the smart board.
Be Broglie’s Hypothesis

• Electrons travel in waves
• All matter travels in waves
  – As ships on a sea
Heisenberg’s Uncertainty Principle

• It is impossible to simultaneously
  determine the position and the velocity of
  an electron (or any other particle)
• Difficult to accept-yes, but get use to it!
  – Any measurement we make will disturb one
    or the other
   The quirky nature of quantum
            mechanics

• Schrodinger wave equation
   The quirky nature of quantum
            mechanics
Things on a small scale behave like nothing
   you have any direct experience about.
      They do not behave like waves.
    They do not behave like particles.
 They do not behave like clouds or billiard
 balls or weights on springs or like anything
       you have ever seen (Feynman).
  The Quantum Electron Cheer
• LEVEL!
• SUBLEVEL!
• ORBITAL!
• SPIN!
The Quantum NUMBER Cheer
• Principle!
• Angular!
• Magnetic!
• SPIN!
 Atomic Orbitals and Quantum
          Numbers
• Quantum Numbers
  – Specifies properties of orbitals
  – Specifies properties of electrons in orbitals
  – Derived from Schrodinger’s wave equation
• They are (Quantum number Cheer!)
  –   Principal Quantum Number
  –   Angular Momentum Quantum Number
  –   Magnetic Quantum Number
  –   Spin Quantum Number
    Principal Quantum Number
• Indicates the main energy level
    occupied by an electron
•   Symbolized by n
•   Values of n are positive integers
    only. 1,2,3 and so on
•   Also called a level or shell
•   There are n subshells/sublevels
    in a shell
• Each level contains n2 orbitals
• Each level contains 2n2 electrons
   Angular Momentum Quantum
             Number
•Indicates the shape of the subshell/sublevel orbitals
  •Shapes will be discussed later


•Known as a “subshell or sublevel”
•Indicated by l and I=(0, to n-1)
•Also represented by letters s=0,p=1,d=2,f=3
•Therefore when n=1, I=0, a s orbital
•Therefore when n=2, I=0,1, an s & p orbital
•Therefore when n=3, I=0,1,2 an s & p & d orbital
•N=4?
     Magnetic Quantum Number
•Indicates the orientation of the orbital
about the XYZ Axis centered on the nucleus
•The number of possible orientations
(orbitals) is determined by the shape of the
sublevel
•S sublevel, 1 orientation, 1 orbital
•P sublevel, 3 orientations, 3 orbitals
•D sublevel, 5 orientations, 5 orbitals
•F sublevel, 7 orientations, 7 orbitals
       Spin Quantum Number

•Indicates the two
fundamental spin states of
an electron
•Every orbital holds a
maximum of two electrons
of opposite spin
              s Orbital
        Shape and Orientation
• Uniform, one possible orientation
• Holds 2 electrons
            p 0rbitals
      Shape and Orientations
• Three p orbitals
• Each hold 2 electrons
• 6 electrons total
            d Orbitals
      Shape and Orientations
– 5 d orbitals
– Each hold 2 electrons
– 10 electrons total
– And f, we to keep it simple it has 7
  orientations an holds 14 electrons

				
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posted:6/20/2012
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