Atomic Structure

• What are isotopes?

  Atoms with same number of protons but different number of neutrons
• How is isotopic data used by physicists?

  Radioactive isotopes can be used to calculate age

  • All living things contain same ratio of Carbon-14 to Carbon-12
  • Carbon-14 is breathed in from the atmosphere
  • After living organism dies, Carbon-14 inside them decays
  • Physicists then use the percentage of Carbon-14 left and compare with isotopic data to calculate age of the decaying living organism
• Specific Charge = Charge / Mass of Ion (Q / M)
• What is the strong nuclear force?

  • Attractive force that holds protons and neutrons together in the nucleus
  • Has a very short range - attractive up to a few femtometres
  • Force = 0 at larger distances (above 3.0 fm)
  • Repulsive at very small distances (below 0.5 fm)
  • A decay particle most likely to be received if the size of nucleus of an atom exceeds 3 fm
• What is annihilation?

  Where a particle and its corresponding antiparticle collide as a result their masses are converted into energy. This energy along with the kinetic energy of the two particles is released in the form of 2 photons
• What is pair production?

  Where a photon is converted into an equal amount of matter and antimatter.

  Can only occur when the photon has an energy greater than the total rest energy of both particles.

  Excess energy converted to kinetic energy
• What are the fundamental forces?

  • Electromagnetic
  • Weak Nuclear Force - responsible for nuclear decay
  • Strong Nuclear Force - holds nucleus together
  • Gravity
• How do electrons know when to repel each other?

  • The interaction is carried out by a particle which is being emitted and exchanged by the electrons called a virtual photon
• What is a gauge boson?

  • An exchange particle for any interaction
• What are the fundamental forces, what are the exchange particles that carry out the interactions and what are the particles affected by them?

  • Electromagnetic: Photons -> All charged particles
  • Weak Nuclear Force: W+,W- bosons -> All particles
  • Strong Nuclear Force: Pions -> Hadrons
  • Gravity: Graviton
• What are virtual particles?

  Particles that exist for a very short time
• What happens in Beta Plus decay?

  • Proton turns into a neutron
  • This happens when quarks inside of a proton release a W+ boson and this W+ boson will turn into a positron and a neutrino