UNIT 3 - Atomic Structure and Periodic Trends

UNIT 3 - Atomic Structure and Periodic Trends

1. * atoms

   • * nucleus
     • outside
       • * electrons
         • - charge
         • m = ~1/2000 amu
           • electrons don't contribute much to the mass of an atom
         • involved in chemical reactions
     • inside
       • * protons
         • + charge
         • m = 1 amu
         • determines element
       • * neutrons
         • no (neutral) charge
         • m = 1 amu
         • affects mass and nuclear stability
     • has most of atom's mass
   • most of its volume is in space where electrons are
   • * ions
     • an atom with a charge
   • * isotopes
     • atoms of the same element with different numbers of neutrons
   • atoms of the same element have the same # of protons
   • [p = e]

2. * Isotope Notation

   • * mass #
     • [p + n]
       • doesn't include e
   • * atomic #
     • [p]
   • * charge
     • [p - e]

3. * Plum Pudding Model

   • majority of space is mass of +
   • electrons float around inside atom
   • *Gold Foil Experiment
     • most particles went through, some deflected at wide angles, and others went backwards
       • if P.P. true --> alpha particles would not have passed through foil
         • P.P. disproved
           • Nuclear Model
             • protons at dense, small, concentrated nucleus
             • electrons revolve around nucleus in wide orbits
             • no way to make predictions off of N
               • Bohr's Nuclear/Planetary Model
                 • electrons move around nucleus in circular orbit
                 • only specific orbits are allowed
                   • an electron in a given orbit has a specific energy
                     • * photons
                       • absorb/give off energy when traveling between orbits
                         • [-Rh/n^2]
                           • electrons farther from the nucleus have larger energy
                           • * ground state
                             • lowest energy orbit
                           • * absorption spectrum
                             • when electrons gain enough energy (the exact difference between the Eh and El) to move to a higher energy level
                           • * emission spectrum
                             • when electrons lose enough energy (the exact difference between the Eh and El) to move to a lower energy level
                 • * orbit
                   • aka discrete energy levels
                 • has several limitations
                   • only works for matter w/1 electron
                     • attraction/repulsion between particles depends on distance between electrons, and if there was more than one electron, the distance would be fluctuating
                   • only works for Hydrogen
                   • the laws of physics disagree
                     • physics predicts that an accelerating charged particle should lose/radiate energy. In the Bohr model, the electron is accelerating because it's moving in a circle, so it should lose energy and crash into the nucleus, destroying the atom and rendering the concept of life impossible
                   • model violates Heisenberg Uncertainty Principle
                     • you cannot tell both the position and momentum/momentum (p = mv)
                   • B's N/P disproved
                     • Quantum Model

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