HONR228Q Notes section f:

  • Basic Atomic Structure

    1. Historical models of the atom

      1. Competing early twentieth century models
        1. Plum pudding model: everything mixed together in "pudding"
        2. Nuclear model: small, heavy nucleus with electrons circling around
      2. Later twentieth century models
        1. Heavy nucleus
          1. Nucleus contains positive protons and neutral neutrons
        2. Electrons outside of nucleus
          1. Electrons form "cloud" around nucleus rather than moving like planets
          2. Electron cloud results from their quantum mechanical wave function
          3. Electron "states" are occupied by only one electron each (Pauli exclusion principle)
        3. Late twentieth century model
          1. Protons, neutrons and electrons are formed from combining "quarks"
          2. Many "elementary particles" discovered and classified using quark model

    2. Structure of the atom

      1. Component parts
        1. Protons: mass mp=1.672623x10-27kg=938.272MeV; charge qp=1.602177x10-19Coulomb = +qo
        2. Neutrons: mass mn=1.674928x10-27kg=939.566MeV; charge qn=0
        3. Electrons: mass me=9.109389x10-31kg=0.511MeV; charge qe=-1.602177x10-19Coulomb = -qo
      2. The nucleus
        1. Contains protons and neutrons, virtually all of the weight
        2. Charged positive
        3. Nuclear size ~10-15meter
        4. Responsible for radioactivity
      3. The atom
        1. Contains electrons in cloud outside the nucleus
        2. Electrons attracted to nucleus by electrostatic (Coulomb) force
        3. Atom has neutral charge: number of protons equals number of electrons
        4. Atomic size 10-10meter for all atoms
          1. Inner electrons shield outer electron so outer electron always sees "nucleus" with charge of +qo
          2. DEMO P3-11: LANGMUIR EXPERIMENT for estimation of atomic size
          3. Oleic acid description (used in Langmuir experiment to determine atomic size)
        5. Atomic forces responsible for chemical and crystal phenomena
      4. Nuclear matter vs. atomic matter
        1. "Nuclear matter" approximately 1015 times density of the atom
        2. Examples: neutron stars and black holes
        3. Earth diameter 8000 miles to 400 feet if earth were nuclear matter
      5. Some definitions and terms
        1. Number of protons in nucleus is atomic number Z
        2. Number of neutrons in nucleus is N
        3. Number of electrons is equal to number of protons in a neutral atom
        4. Atomic weight W is number of protons plus neutrons: W = Z + N

    3. Electron States and the Periodic Table

      1. Electrons fill up "energy levels" beginning with the lowest energy (most tightly bound)
        1. Electron has two "spin" states: up or down
          1. Electron does not actually spin on its axis
          2. Electron behaves and interacts like it were spinning
        2. Electron states have three quantum numbers:
          1. "n" describes average radial position of the wave function
          2. n = 1, 2, 3, 4, .....
          3. "l" describes azimuthal distribution of the wave function
          4. For each n state, l = 0, 1... up to (n-1)
          5. "m" describes sub-set of the azimuthal distribution
          6. For each m state, electron spin = +1/2 or -1/2
          7. Two electron states per orbital state: spin up and spin down
          8. Each state can hold only one electron (Pauli exclusion principle)
      2. The Periodic Table of Elements
        1. Flash animation set to the "The Elements" by Tom Lehrer.
        2. WebElementsTM periodic table: Scholar edition: Home page
        3. David's Whizzy Periodic Table
          1. Animated atoms and nuclei
          2. Atomic electron states illustrated
          3. Spectra for each element shown
          4. All "click and play"
          5. Have fun playing with the elements!
        4. Links to web-based periodic tables
          1. Detailed periodic table for study using the web
          2. Links in table provide great detail about each element
        5. The Periodic Table of Dessert
        6. The Man Show Periodic Table (R Rated)
        7. DEMO P3-01: PERIODIC CHART
        8. Relates shell structure atomic properties
        9. Periodic chart uses average atomic weight for all isotopes
        10. States filled in order of increasing energy until shell is complete, then next shell is filled
        11. Full atomic electron shells: 2, 8, 8, 18, 18, ....
        12. Binding energy greatest for electron completing each shell
        13. Element, orbital label, and n,l,m values for final electron as shells are filled:
          14. element orbital n l m
          H 1s1 1 0 0
          He 1s2 1 0 0
          Li 2s1 2 0 0
          Be 2s2 2 0 0
          B 2p1 2 1 0
          C 2p2 2 1 0
          N 2p3 2 1 1
          O 2p4 2 1 1
          F 2p5 2 1 1
          Ne 2p6 2 1 1
        14. Table of Condiments That Periodically Go Bad
      3. Standing wave nature of electron states
        1. Experiments
          1. DEMO G3-28: SUSPENDED SLINKY
          2. DEMO H3-61: BEAKER BREAKER
          3. DEMO H3-62: TEACUP STANDING WAVES
        2. Conclusions
          1. Slinky spring demonstrates linear standing waves
          2. Beaker breaker demonstrates linear circular waves
          3. Atomic electron states are similar to standing waves seen
          4. Each standing wave electron state has specific binding energy
          5. Have fun playing with the elements!!
        3. P3-02: ATOMIC ELECTRON ORBITAL MODELS
          1. Show basic configuration for various electron states
        4. SLIDES OF ATOMIC ELECTRON STATES
          1. Illustrate 3-D standing wave states of atomic electrons
          2. Computer generated: density of dots is value of the wave function at each location
      4. The Franck-Hertz experiment
        1. Experiment
          1. DEMO P3-41: FRANCK-HERTZ EXPERIMENT
          2. Shoot electrons through cloud of mercury vapor
          3. Measure electron current as function of incoming electron energy
        2. Analysis
          1. Current shows peaks and valleys
          2. Valleys are absorption when moving electron energy equal to integral number times shell binding energy

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