XIII. Radiation

1. emission of radiation energy
   1. alpha
      • 2 protons, 2 neutrons
      • mass = 4, charge = +2
      • large size
      • don’t penetrate much
      • lots of kinetic energy so can damage surfaces (living tissue)
      • quickly pick up electrons and change to helium
   2. beta
      • 1 electron
      • no mass, charge = -1
      • small particle
      • penetrates light material
      • eventually absorbed as regular electron into whatever they hit
   3. gamma
      • pure energy
      • no mass or charge
      • can penetrate almost anything
      • very dangerous
   4. transmutation
   5. spontaneous
   6. half life

1. strong nuclear forces
   1. strong force
   2. only attractive
   3. very short distances (nearly touching)
   4. effective in small nuclei where all protons and neutrons are close
2. electro-magnetic forces
   1. weaker than nuclear forces
   2. works over larger distances
   3. repulsive in nuclei (only + charges)
   4. increased number of neutrons reduces the repulsive effect
   5. overwhelms attractive nuclear forces in large nuclei (making them unstable)
3. neutrons instability
   1. neutrons are unstable in isolation
   2. decompose into a proton and an electron (beta particle)
   3. stable in the presence of a proton
4. results
   1. small nuclei tend to be stable, held together by strong nuclear forces
   2. as nuclei grow, they often add a greater proportion of neutrons to decrease the repulsion of e-m forces
   3. if nucleus gets too large, the ratio of neutrons to protons causes some neutrons to become unstable
   4. all elements greater than 83 are unstable

1. fission
   1. a. collision of a neutron and atoms – “splits” the atom
   2. releases more neutrons which then split more atoms
   3. chain reaction
   4. requires a critical mass for explosion - neutrons escape out the surface in smaller pieces.
   5. for elements larger than iron, energy is released because nucleons in proudct elements have less mass than original nucleons (mass converted to energy)
   2. fusion
   1. combine two small nuclei (must be moving very fast (ie be very hot)
   2. combination has smaller mass than the 2 originals (up to iron)
   3. loss of mass is converted to energy