unstable nuclei and radioactive decay

    Cards (10)

    • Nuclear radiation is emitted by unstable nuclei to become more stable , this is called radioactive decay and is a random process.
    • Alpha decay:
      • consists of two protons and two neutrons
      • nucleon number decrease by four and proton number changes by 2
      • has the highest ionizing power
      • range of 5cm
      • stopped by paper
    • Beta minus decay:
      • a fast moving electron and an anti-neutrino
      • nucleon number stays the same but proton number increase by one
      • neutron becomes a proton
      • high ionizing power
      • 1 meter range
      • stopped by aluminum
    • Gamma radiation:
      • short wavelength but high frequency electromagnetic radiation
      • loses energy
      • low ionizing power
      • range of few km
      • stopped by several cm of thick lead
    • the neutrino was hypothesized to account for conservation of energy in beta decay , a certain amount of energy should be transferred by beta decay , but beta particles had a range of energies instead of one value. so another particle was suggested that may carry away excess energy. this was the anti-neutrino
    • neutrino have very little mass and zero charge , making them hard to detect.
    • exchange particles and corresponding forces:
      • gravity = graviton
      • electromagnetic = virtual photon
      • strong nuclear force = gluon for quarks or pions for all other hadrons
      • weak nuclear force = w+ and w- bosons
    • properties of forces:
      • gravity = attractive force between any two objects due to their masses
      • electromagnetic = acts between objects with charge - repulsive when the charge is the same and attractive when charges are opposite
      • strong nuclear = only acts on a set of particles called hadrons ; holds protons and neutrons together in a stable nucleus
      • weak nuclear = extremely short range , force that acts on hadrons and leptons , involved in radioactive decay.
    • what can carbon-14 be used for?

      can be used in the carbon dating of fossils to calculate age
    • whats is the equation for electron capture?
      p+e- --->n+v