radioactivity

• what does an atom consist of?

  a positively charged nucleus and negatively charged electrons moving around the nucleus
• strong attractive forces between the positively charged nucleus and negatively charged electrons hold the electrons to the atom
• the nucleus of an atom consists of a proton and neutron
• a proton is positively charged
• a neutron does not carry any charge
• the nucleon number is the total number of protons and electrons in the nucleus of an atom
• the atoms of the same element can have the same number of protons but different number of neutrons. hence, they are isotopes
• nuclear decay is known as radioactivity
• radioactive decay is the spontaneous transformation of an unstable nucleus into a more stable nucleus by the release of radiation
• radioactive decay is unpredictable and can't be controlled
• alpha 


  a heavy nucleus emits an alpha particle. they are highly ionising and weakly penetrating. can be stopped by a sheet of paper
• beta


  a neutron turns into a proton and emits a beta particle
• the nucleon number of an alpha particle decreases by 4 and the proton decreases by 2
• the nucleon number of a beta particle remains the same and the proton number increases by 1
• gamma radiation is also emitted after an alpha or beta particle is emitted
• beta particles are moderately ionising and moderately penetrating, they can be stopped by aluminium foil
• gamma particles are lowly ionising and highly penetrating. they can be stopped by centimetres of lead
• background radiation are non ionising radiation
• background radiation is radiation with high energies that can knock off electrons from atoms to form ions
• sources of background radiation: cosmic rays, radioactive materials, and natural radiation
• sources of background radiation from space

  cosmic rays include high energy charged particles that penetrates the atmosphere
• sources of natural background radiation

  food and drinks that are high in potassium, rocks, radon gas
• artificial background radiation sources

  medical x-rays, building materials, waste products from nuclear power stations
• emittion of radiation is spontaneous and random in motion'
• gamma decay radiation


  nucleon and proton remain the same