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Last lecture before test 1!

Announcements

  • Test tonight
    • Only like 20 Questions
    • Pencil, eraser, photo-ID
    • Audio 0:00:31.902459
    • No, no, no phones
    • You should know all the prefixes
      • how many ml in a liter
      • Any imperial to metric will be given
      • 12 in to a foot and 3 ft to a yard

Clicker Question

  • Find wavelength of electron with velocity of 1.8710^7 m/s and mass of 9.1110^-31 kg
  • Audio 0:10:28.871589
  • .0388 nm

Wave Nature of Particles

  • Audio 0:15:57.282705

Electron Diffraction

  • Audio 0:19:15.239273
  • Transmission Electron Microscope
  • If electrons behave only like particles, there should be only two bright spots on the target.

Trajectory Vs Probability

  • Audio 0:21:20.562074
    • If you know the forces acting on an object with classical trajectory, you can tell exactly where it will land
    • With electrons, you can only know with a degree of certainty where it will be

Uncertainty Principle Demonstration

Heisenberg’s Uncertainty Principle

  • Heisenberg stated that the product of the uncertainties in both the position and speed of a particle was inversely proportional to its mass.
    • x = position, Δx = uncertainty in position
    • v= velocity, Δv = uncertainty in velocity
    • m=mass

  • This means that the more accurately you know the position of a small particle, such as an electron, the less you know about its speed, and vice versa.

  • Stopped short for practice questions

Q1

  • An element has three stable isotopes with masses of 27.977 amu, 28.976 amu, and 29.973 amu. The heavier two isotopes have an abundance of 4.68 % and 3.09 %. What is the atomic mass of the element?

Q2

  • Rank in order of increasing mass
    • proton < neutron < electron
    • proton < electron < neutron
    • electron < neutron < proton
    • electron < proton < neutron

(answer is C)

Q3

  • How many protons, neutrons, and electrons are in isotope ^65_28X
    • 36 neutrons, 29 protons, and 29 electrons

Q4

When waves of equal amplitude from two sources are in phase when they interact, it is called => constructive interference

Q5

What is the frequency of an electron with wavelength 486.1 nm? +