Nuclear Physics:

Radioactive decay:

  • Regardless of any circumstances radiation does not change: temperature, sound, chemical conditions, etc.
  • These particles were good at ionizing electrons: “knocking off” electrons (charging)
  • Element notation:  
  • A=mass number
  • Z= atomic number
  • X= individual element
  • No two elements are the same
  • Isotopes: same element with different mass… atomic number, different mass number
  • Unless otherwise specified, the element will be assumed to be electrically neutral, so there will be the same number of electrons as there are protons.
  • Protons and neutrons: nucleons 
  • Nucleus stays together by strong nuclear force.  Sometimes force is overcome and atom is unstable.  Unstable isotopes: RADIOISOTOPES.

This is because when there are more protons, lots of protons repel as the force does not hold all the protons together.

  • Different ionizing radiation: α, β and γ (alpha, beta and gamma)

α Radiation:

  • Most powerful.  Approximately 5MeV ← unit of energy: Mega Electron Volt.  
  • Ionizes things almost straight away
  • Stopped easily: air, paper, skin
  • Very dangerous if inhaled or indigested. (alters DNA, ionizes)
  • Electrical charge of +2
  • Very heavy, approximately a Helium atom’s weight.
  • Is able to travel at up to approximately 5% of c (where c is the speed of light)
  • Radiation is very damaging and very fast, (50 million km/hr)
  • Because it is so fast, generates heat: burning/melting
  • Alpha radiation has no electrons (ionized) and is just a Helium Nuclei.
  • 42He2+
  • eg. 23592U 23190Th + 42α + energy    ) numbers always work out, add up/balance
  • The ‘energy’ is gamma radiation
  • Also can be written as

23592U                 23190Th

β Radiation:

  • fairly powerful ≈ 1MeV
  • not as damaging as alpha
  • takes a few meters of air, few cm of paper, mm of skin, very thin metal sheet (e.g. aluminum) to stop it
  • charge of -1
  • small particles, weigh as much as an electron
  • travel at 99%c
  • beta radiation is actually highly energetic electrons
  • 0-1e
  • β radiation occurs when a neutron decays into a protons and an electron and a little particle called an anti-neutrino.  
  • Occurs when there are too many neutrons (isotope is too heavy).  Proton remains in nucleus, electron rockets out very fast.
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i.e. 10n 11p + 0-1e + νe  

  • 146C 147N + 0-1β + νe + energy

γ Radiation:

  • less powerful ≈ 0.1MeV
  • Can pass through many cm of lead
  • No charge
  • No mass
  • Travels at the speed of light
  • Given out in large quantities (other two aren’t)
  • Gamma rays are actually electromagnetic radiation of high frequency, i.e. high energy light
  • After decays and interactions, nuclei may have excess energy, therefore being unstable.  This is where they release a γ particle with the excess energy.  Often happens with the decay.
  • E.g. 13153I → ...

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