Review of Atomic Theory thus far by akimbo

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									    Review of Atomic Theory thus
                 far
   Dalton (1766-1844)
   Thomson (1856-1940)
   Rutherford (1871-1937)
   Where are those electrons?




                    Electron in Atoms   1
Bohr Model
    Niels Bohr model (1885-1962)
   Electrons arranged in concentric circular orbits
    (planetary model)
       Levels hold different numbers of electrons
            2, 8, 8 – 1st 3 levels
   Staircase, ladder analogies – discrete energy
    levels
   Quantum – energy required to move an electron
    from present level to next higher one
   Levels can be unequally spaced
       Higher the electron, steps become closer together


                                      Electron in Atoms     3
        Quantum Mechanical Model
   Schrodinger’s model (1887-
    1961)
      Modern description of the
        electrons in atoms –
        Quantum theory
   Restricts energy of electrons to
    certain values, but does NOT
    define specific orbits
   Estimates probability of finding
    electrons in certain positions
   Electron cloud model




                                Electron in Atoms   4
Energy Levels and Atomic Orbitals
   Principal energy levels (n)
   Sublevels
   Atomic orbitals (each can hold 2 electrons)
       S, P, D, F
   What do Atomic Orbitals look like?
       http://www.shef.ac.uk/chemistry/orbitron/
       http://web.mit.edu/3.091/www/orbs/


                        Electron in Atoms           5
           Energy Levels/Orbitals
   1st energy level
       1 1S orbital
   2nd energy level
       1 2s, 3 2p’s
   3rd energy level
       1 3s, 3 3p’s, 5 3d’s
   4th energy level
       1 4s, 3 4p’s, 5 4d’s, 7 4f’s

                          Electron in Atoms   6
    How do the electrons arrange
           themselves?
   Electron
    configurations
       Ways in which
        electrons are arranged
        around the nuclei of
        atoms
   3 Rules of Guidance:
   Aufbau principle
       Electrons enter orbitals
        of lowest energy first
       Show filling order

                            Electron in Atoms   7
            3 Rules of Guidance:
   Pauli exclusion principle
       Atomic orbital can only hold two electrons
       Electrons must be of opposite spin
   Hund’s rule
       Electrons will fill each orbital in a sublevel
        before pairing up to complete orbital
   Examples: B, F, any element!
       Tutorial

                          Electron in Atoms              8
           Exceptions to Electron
              Configurations
   Chromium
       Special stability with half filled orbitals
   Copper
       Special stability with full orbitals
   Electron configurations of ions?
       Try O2-, Na+




                           Electron in Atoms          9
    Background for Quantum Theory
   Properties of Waves
   Crests, Troughs
   Amplitude (A)
       Height of the wave from
        origin to crest
   Wavelength (lambda)
       Distance between crests,
        troughs, or point
   Frequency
       Number of wave cycles to
        pass point per unit of time
       Units – cycles per second =
        hertz
    Using Frequency, Wavelength,
       Speed of light equation
   Velocity, frequency, and wavelength
       c=λν
   Frequency = speed of light/wavelength
       Note relationships between variables- direct/indirect
        proportions
   Example:
       frequency of yellow light = 5.10 x 1014 Hz, calculate
        the wavelength.
   Example:
       What is frequency of radiation whose wavelength is
        5.00 x 10-6 cm?
                            Electron in Atoms                   11
Electromagnetic Spectrum Chart




           Electron in Atoms     12
                  Atomic Spectrum
   EM spectrum
       Radio waves, microwaves, visible light, infrared, UV light, X-rays,
        gamma rays
   Light as a continuous spectrum
       Light – colors are different frequencies and wavelengths
       Sunlight through prism – light separates into spectrum of colors
       ROYGBIV
   Many expecting continuous spectrum for atoms
       Instead, a line spectrum was observed
   Each element has a unique line spectrum




                                Electron in Atoms                        13
                   Atomic Spectra
   Ground state configurations
   Excited state configurations
       Tutorial
   Energy emitted when electrons return
    from excited states
   E = h v (energy of photons)
       h = 6.62 x 10-34 J s (Planck’s constant)
       Energy absorbed or emitted proportional
        to the frequency of radiation
                        Electron in Atoms          14
                Practice
   Also referred to as Photoelectric
    Effect
 What  is energy of photon of
  microwave radiation whose
  frequency is 3.20 x 1011 s-1
 Calculate the energy (in Joules) of
  a photon whose frequency is 5.00
  x 1015 s-1

                   Electron in Atoms    15
END




Electron in Atoms   16
      Lab #2 – A/W-3: Observing a
           Chemical Reaction
   Recording observations, differences
    between observations and interpretations,
    quantitative vs. qualitative observations
   Techniques: Recording data real time
   Safety: Goggles
   Lab Analysis Questions: All except Design
    Experiment


                    Electron in Atoms       17
    Lab #3 – A/W 20: Flame Tests
   Objectives:
      Observe flame test for different metallic ions

      Identify an unknown metal using flame test

   Technique Notes:
      Wooden splints instead of wire loops (No HCl)

      Unknown contains mixture of salts

   Safety: Don’t let wooden splints burn more than
    necessary. Watch contamination.
   Lab Analysis Questions: All

                       Electron in Atoms            18
   de Broglie’s equation
       All matter exhibits wavelike motions
   Heisenberg uncertainty principle
            Impossible to know exactly both the velocity and
             the position of a particle at the same time




                             Electron in Atoms                  19

								
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