P2- radioactivity

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observing nuclear radiation

  • nuclei of radioactive substances is unstable and they become stable by  radioactive decay- they emit radiation and turn into other elements
  • three types of radioactive radiation- alpha, beta and gamma
  • radioactive decay is a random process that isnt affected by external conditions
  • background radiation is always around us- its from radioactive stuff in the environment, space and devises like x-ray tubes

discovery of the nucleus

  • the plum pudding model- atoms are spheres made of positive charge with electrons stuck in them
  • rtherford, geiger and marsden created the alpha particle scattering experiment- they fired alpha particles at thin gold foil
  • most passed through- most of atom is empty space
  • some were deflected by small angles- nucleus has positive charge
  • a few rebounded- nucleus has a large mass and very large positive charge

nuclear reactions

  • alpha decay- nucleus looses 2 protons and 2 neutrons which are emitted as alpha radiation
  • beta decay- a neutron changes into a proton and a electron and the electron is instantly emitted as beta radiation
  • relative mass of an electron= 0.0005
  • if an atom gains or looses an electron is becomes charged and is called an ion
  • all atoms of same element have same no. of protons but atoms of same element with different number of neutrons are clled isotopes
  • when a nucleus emits an alpha particle the atomic number goes down by 2 and…

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