physics

• Everything is made up of atoms
• atoms


  Small, have a radius of 1x10^-10
• Atoms are mostly empty space
• Nucleus


  Made up of protons and neutrons
• Proton


  Positive charge (1e)
• Electron


  Negative charge (1e), orbits around the nucleus
• Atoms are neutral because they have an equal number of protons and electrons
• Excitation


  Atom absorbs electromagnetic radiation and can move electrons away from nucleus
• de-excitation

  Electron moves closer to nucleus and emits electromagnetic radiation
• Democritus proposed a theory that objects can be cut up until they are as small as possible (atoms)
• John Dalton's theory: atoms are solid spheres, each element has its unique sphere
• Thomson's theory: existence of electrons, contained positive and negative charge (discovery of plum pudding model)
• Rutherford's theory: existence of the nucleus of atom, mass in positive nucleus (gold foil experiment)
• Alpha particles


  Positively charged particles
• Alpha decay


  1. Most decreases by 4

  2. Atomic number decreases by 2

  3. 2 protons and 2 neutrons join up to form an alpha particle, which is emitted
• In beta decay, a neutron decays to a proton, an electron, and an antineutrino
• In gamma decay, the atomic number and mass stay the same
• Uses of radioactivity


  • Paper/content mill
  • Radioactive tracer sound is used on one side of the material and a detector on the other side
• If too much radioactivity is going through, then the material is too thin and the holes open up a bit to make the material leak
• If not enough is detected, then the rollers compress to make the material thinner
• Contamination is when lots of radioactive particles nuclei are on you
• Irradiation is being exposed to radioactive rays, and can be harmful