Ch.28: Read Section 1 Ch.29: 4, 7, 27, 41. Ch.30: Read Sections 1-3.

2 Matter Waves DeBroglie: = h/(mv), noticeable for small momentum, e.g. electron Ex. Electron, v = 4000m/s: = (6.63x Js)/[(9.1x kg)(4000m/s)] = um

3 stationary states DeBroglie: electron orbits are integral multiples of the matter wavelength r

4 Rutherford Scattering positive radiation on metal foil Video simulation Uniform positive solid would cause similar deflections actual result: wide variation Conclusions: Solid not uniform But have small +nuclei

5 symbols Z = Atomic Number = #p A = Mass Number = #p + #n X = Element Symbol full symbolic form: Example: Helium =

6 radioactivity “alpha” (helium nucleus) “beta” (electron) “gamma” (photon) thickness of lead required to shield: alpha (~0.01mm), beta (~0.1mm), gamma (~100mm)

Activity & Decay Decay: A  B + radiation Half-life: time when half of A remains Activity ~ Decay rate Activity large when half-life small Activity small when half-life large 7

8 Radiation parameters N = number of atoms = decay constant T 1/2 = half-life T 1/2 = 0.693/. Activity = - 

9 Example 1 Given No = 32,000, half-life = 1.5 days. Calculate N after 4.5 days  = 0.693/T 1/2. = 0.693/1.5days.

Alternate Formula Given No = 32,000, half-life = 1.5 days. Calculate N after 4.5 days 10

Example 2 Given No = 64,000, half-life = 44 min. Calculate N after 5 hours (300min.) 11

12 nuclear stability regulated by neutrons higher Z atoms are less stable Z = 83 (Bismuth) largest stable atom Z >= 84 (Polonium) are unstable (radioactive)

13 nuclear binding energy mass atom < mass of parts difference is called “mass defect” binding energy ~ mass defect Shifts to more stable states release energy, e.g. book falls over Fission: broken atoms more stable Fusion: joined atoms more stable Fission simulation

14 End

15 nuclear transformations alpha: Z reduced by 2, A reduced by 4 beta: Z increases by 1, A stays same examples:

16 Light Photon Smallest amount of EM wave Carries energy and momentum constant h is “Planck’s” Constant

17 Uncertainty in p, E Limiting one variable causes another variable to become more uncertain. Heisenberg Uncertainty Principle

18 Photon Momentum p = h/ SI units: h = 6.63x J·s Ex. momentum of a photon with wavelength 130 nm: p = h/ = (h = 6.63x J · s)/(130x10 -9 m) = 5.1x kg · m/s [J · s/m = N · m · s/m = N · s = kg · m/s]

19 Electron Theories Electrons determine physical properties including: resistivity hardness light emission and absorption

20 quantum mechanical picture involves 4 quantum numbers (3 more than the Bohr model) quantum-mechanical model allows for electron states with zero angular momentum

21 electron shell theories electrons in stable ‘orbits’ collisions cause electron “planets” to move to larger, higher energy, orbits “light” energy emitted when they drop back to their original smaller orbits