radioactivity

• alpha particle - a positively charged particle consisting of 2 protons and 2 neutrons
• beta particle - a high speed electron that the nucleus emits when a neutron converts into a proton
• chain reaction - the process of neutrons released by a fission reaction, being absorbed by another unstable, large nuclei, and inducing further fission
• electrons - a negatively charged atom, found in different energy levels, around the nucleus
• activity - the rate at which an unstable nuclear decays. The activity of a radioactive sources of reduced over time
• half-life - the time taken for half of the atoms in a sample to decay
• nuclear fusion - the joining together of two light atomic nuclei to form one heavier nucleus with the release of energy.
• background radiation -radiation that is found in small quantities all around us and originates from natural sources such as rocks and cosmic rays, as well as from manmade sources such as nuclear weapons testing and accidents
• becquerel - unite of radioactive activity
• bohr model - a model of the atom that suggests that electrons orbit the nucleus at set distances. He suggested electrons were in electron shells around the nucleus rather than just floating in clouds around the nucleus
• nuclear fission - the splitting of a large and unstable nucleus into two smaller and more stable nuclei to produce energy. This is the method currently used in nuclear power stations
• PET scanner - a medical imaging device that uses radioactive tracers and detectors to form internal body images
• plum pudding model - an old model of the atom that represented the atom as a ball of positive charge, with negative charges distributed throughout it

  • made by JJ Thompson - his theory proves atoms have a neutral charge as the positive protons and the negative electrons cancel
• random nature of radioactive decay - you cannot predict which nuclei in a radioactive sample will decay next, or when the next decay will occur : it's a random process
• • there's an equal amount of protons and electrons
• electron :

  • relative charge = -1
  • relative mass = 0.0005
  • they exist in a distinct energy level, the levels can change by absorption or emissions by radiation
• ionising radiation :

  • damage body cells can mutate leading to cancer
  • CT scans - x ray scans combine to produce images of the body and its bones
  • radiotherapy - radiation focused to kill cancer cells (chemo therapy)
• irradiation - object is exposed to radiation without becoming radioactive
• geiger muller tube measures the count rate of nuclear decay
• background radiation :

  man-made = nuclear weapon testings and accidents

  natural = rocks and cosmic rays from space
• nuclear fission - process of nucleus splitting into two smaller nuclei after absorbing neutrons which releases more neutrons

  • uncontrolled chain reactions are used in nuclear weapons
  • neutrons released in one fission induce further fission - creates chain reaction
• nuclear fusion - joining of two light nuclei into a larger nucleus

  • mass is converted into energy in the alpha form of radiation
  • to occur it requires very high temperatures and pressures