topic p4- atomic structure

• plum pudding model

  
• plum pudding model

  • a pool of positive charge
  • negative particles floating around it
• current model

  
• current model

  • a nucleus at the centre, where most of the mass is
  • neutron, proton and electron were discovered
  • mostly empty space
  • electrons orbiting the nucleus, at different energy levels
• rutherford's alpha scattering experiment

  
• results of rutherford's aplha scattering experiment

  • most particles travelled straight through the foil
  • some were deflected slightly
  • very few were deflected straight back/ significantly
• conclusions of rutherford's alpha scattering experiment

  • the atom is mostly empty space
  • a small mass in centre of the atom
  • this mass must be positive, due to the repulsion force causing deflections
• isotopes

  • atoms with:
  • the same number of protons
  • but different number of neutrons
  • charge doesn't change
  • mass does change
• ions

  • atoms with:
  • the same number of protons
  • but different number of electrons
  • charge does change
  • mass doesn't change
• what types of radiation are there

  • alpha
  • beta
  • gamma
• alpha

  
• alpha

  • when an alpha particle is emitted from the nucleus
  • strongly ionising
  • doesn't travel far in air (few cm's)
  • stopped by paper
  • used in smoke detectors
• beta

  
• beta

  • when a fast moving electron is released by the nucleus
  • moderately ionising
  • travels further in air (few metres)
  • stopped by aluminium
  • used in material thickness testing
• gamma

  
• gamma

  • when an electromagnetic wave is released by the nucleus
  • weakly ionising
  • travels far in air
  • stopped by lead
  • used in sterilising equipment
• half life

  time taken for the number of radioactive nuclei to half
• half-life info

  • radioactive sources give out radiation as it decays
  • radiation is measured with a geiger-muller counter
  • it is an entirely random process
  • activity is the rate at which the source decays
• half-life graph example

  
• radiation risks

  • irridation
  • contamination
• irridation

  exposure to radiation
• irridation info

  • a risk from mostly beta or gamma sources as they can penetrate skin
  • can be reduced by keeping sources in lead lined boxes
• contamination

  radioactive particles getting onto objects
• contamination info

  • alpha radiation is the biggest risk of it as they do damage in a localised area
  • it can be prevented wearing correct PPE such as gloves or special suits