radioactivity

• what is the mass of sub-atomic particles called

  atomic mass unit - amu
• what do neutrons do

  they hold protons together making the nucleus stable
• what is an isotope


  Different forms of the same element with the same number of protons but different nucleon number
• An unstable nucleus will emit...

  radiation
• Two possible reasons why a nucleus may be unstable

  Too much energy in the nucleus and the wrong number of particles in the nucleus
• What do unstable nuclei do?

  To make themselves stable, they throw out particles of energy from their nucleus
• Throes out particles or energy from its nucleus is referred to as:_ and its said to disintegrate


  Radioactive decay
• The daughter cell is an atom of a new element 


  .
• what ionisation


  the charging of nearby particles
• Alpha radiation mass and proton number

  4,2
• Betha radiation mass and proton number

  0,-1
• Gamma radiation mass and proton number

  0,0
• Alpha radiation:

  Emission of particles from the nucleus of an unstable atom
• Betha Radiation:

  Emission of highly energetic electron
• Gamma Radiation:

  high-frequency waves at the end of the electromagnetic spectrum, emitted from the nucleus
• Alpha has _ ionisation power and so cannot penetrate through paper/skin


  high
• Gamma has _ ionisation powers and so can be stopped by a thick layer of lead


  low
• Betha has_ ionisation power and so can be stopped by an aluminium sheet


  medium
• What apparatus is used to detect radiation?

  GM-tube and counter measured in counts per minute
• Half life:

  Time taken for half of the radioactive particles to decay
• How to find half half-life

  Plot a graph of count per minute against time
• Name a few examples of background radiation

  Cosmic radiation and rock and soil
• Corrected count rate

  total radiation - background radiation
• Uses in Medicine:

  high count rate and short half-life. Kills cancerous cells. Since it must penetrate through the skin ideally gamma is used
• uses in Industry:

  To detect the thickness of materials. Half-life should be long so the source doesn't decay quickly. Beta particles are used
• carbon dating

  The older the objects the less radiation it'll release
• smoke detectors

  Alpha particles ionise the air so that it conducts electricity and a small current flows. Smoke would absorb the alpha particles so the current reduces and the alarm will go off. Long half life so it won't need to be changed regularly. Alpha radiation is used as it cannot penetrate the case of the detector and can also strongly ionise the smoke.
• why cant gamma ionise smoke

  it doesnt have any chage