P4 - Atomic Structure

P4 - Atomic Structure

1. atom

   • meaning: uncuttable ('atomos')
   • transfers when rubbed together creating static
   • named by Democritus

2. Atom Structure

   • nuetron
     • charge= 0
     • mass= nearly 0
   • Nucleus
     • proton
       • charge= positive
       • mass= 1
     • electron
       • charge= negative
       • mass= 1
     • 1/10,000th the size of an atom

3. radiation

   • types of radiation
     • beta
       • charge= 1-
       • penetration = stopped by Aluminium foil, few metres in air
       • mass= 1/1832
       • ionisation= fairly strongly ionising
     • alpha
       • charge = 2+
       • penetration = stopped by skin ,paper, few cm of air
       • mass= 4
       • ionisation = very strongly ionising
     • gamma
       • charge = 0
       • penetration = stopped by thick lead, few metres of concrete
       • mass = 0
       • ionisation = weakly ionising
   • half life radiation
     • a measure of time
     • the time taken for half the substance to decay
     • half lives will make a radioactive substance less hazardous over time
       • fewer unstable atoms
   • uses for radiation
     • medical equipment and treatment
     • smoke detectors
     • sterilizing food
   • radioactive decay is random and spontaneous

4. nuclear fission and fusion

   • fission
     • the splitting of a nucleus into 2 smaller nuclei
   • fusion
     • when two small nuclei fuse (join) together to create a larger nucleus
   • energy is released
   • example process
     • uranium absorbs a neutron
       • krypton
       • barium
       • 3 neutrons
         • chain reaction
         • energy

5. models of an atom

   • nuclear model
     • has a nucleus
     • electrons in shells
   • plum pudding model
     • 1898
     • ball of positive charge
       • electrons scattered all over

6. irradiation & contamination

   • irradiation
     • object being exposed to radiation
   • contamination
     • radiation particles transfering to object