atomic structure

Cards (41)

  • radius of an atom

    1 1010 m1\cdot\ 10^{-10\ }m
  • radius of an nucleus

    less than 1/10000 of the radius of an atom
  • nucleus is where most of the mass is concentrated
  • energy levels futher away from the nucleus have alot of energy
  • when electrons absorbs electromagnetic radiation (eg. light) electrons move to a higher energy level
  • when an atom emits electromagnetic radiation the electrons return back and move to a lower energy level
  • radioactive decay happens when an isotope with an unstable nucleus emits radiation to become stable
  • carbon 14 is an example of a radioactive isotope
  • radioactive decay is a random process
  • ACTIVITY
    • activity is the rate at which an unstable nucleus decays
    • it is measured in bequerels
    • 1Bq = 1 decay per second
  • activity can be measured using a geiger-muller tube
  • count rate is the number of decays recorded each second by a detector
  • alpha particles ( α\alpha )
    • same as a helium nucleus
    • 2 protons
    • 2 electrons
  • beta particles ( β\beta )
    • electron ejected from the nucleus at high speeds
    • formed whena neutron turns into a proton then an electron
  • gamma ray ( γ\gamma )
    • electromagnetic radiation
  • another example of a type radiation emitted are neutrons
  • beta particle:
    • travels 15cm in air
    • stopped by a mm of aluminium
    • quite strongly ionising
  • gamma rays:
    • travels several metres
    • stopped by several cm of lead
    • weakly ionising
  • alpha decay
    • loses He24He^4_2
    • mass number decreases by 4
    • atomic number decreases by 2
  • beta decay
    • emits e10e^0_{-1}
    • mass number stays the same
    • atomic number increases by 1
  • half-life
    • time taken for number of nuclei to halve
    • time taken for coun rate (or activity) to halve
  • radiation can be ionising this can increase the risk of cancer
  • precautions of ionising radiation
    • for alpha radiation wear gloves
    • for beta and gamma radiation wear a lead apron
    • using a moniter to see how much radiation is being recieved
  • contamination
    • alpha particles are highly ionising but easily stopped from entering by your skin cells however it is very dangerous when inhaled or swallowed
    • beta particles are less ionising but highly penetrating
    • gamma rays are weakly ionising and pass in and out the body
  • peer review:
    • scientists explore the effects of radiation
    • they publish and share their findings
    • the findings are then checked by other scientists
  • geiger-muller tubes can detect back round radiation
  • natural sources of backround radiation:
    • certain rocks such as granite
    • cosmic rays from space
  • man-made sources of backround radiation:
    • nuclear weapons testing
    • nuclear accidents
    • medecine
  • doses of radiation is measured by
    • sieverts (Sv)
  • exploring internal organs using a tracer :
    • eg. to check the thyroid glands which absorb iodine
    • patients drink radioactive iodine which emit gamma rays
    • too much or too little absorption will indicate an illness
  • you can even do a bone scan using tracers to find tumours
  • a controlled chain reaction is used in nucleus reactors
  • uncontrolled chain reactions are used in nuclear explosions
  • nuclear fusion
    • 2 light nuclei (hygdrogen) join to form a heavier nuclei
    • some of the mass is converted into energy which is released as radiation
    • this is the process that releases energy in stars like the sun
    • this is not a chain reaction
  • what effects exposure:
    • occupation - cabin crew exposed to cosmic rays
    • location - cornwall
  • irradiation
    • irradiation is when an object is exposed to radiation
    • the object does not become radioactive
    • irradiation is used to sterilise medical equipment if it cant be heated up
  • issues with tracers:
    • they must emit radiation that can pass in and out the body
    • must not be highly ionising
    • must not decay into another radioactive isotope
    • must have a short half life
  • contamination
    • contamination is when unwanted radioactive isotopes end up on other materials
    • this is hazardous and will decay leading to ionising radiation
  • radiotherapy:
    • destroy cancers
    • gamma rays destroy cancers
    • ! - healthy tissues may be damaged
    • radioactive rods inserted will cause less damage to healthy tissues
  • alpha particles:
    • travels only 5cm in the air
    • stopped by paper
    • highly ionising