Radioactivity

• electrons are found in shells. if electrons absorb EM waves, they can move to a higher energy level. they return once they have lost that energy. if there are no more shells, they are emitted which releases light
• Radioactive decay is when an unstable nucleus needs to give out radiation to become stable. this is a random process
• the activity measures radioactive decay and is measured in becquerels (Bq) using a Geiger-muller tube.
• Alpha particles properties


  helium nucleus, highly ionizing, travels 5cm in air, stopped by paper
• beta properties


  when an electron is emitted from nuclei. moderately ionizing, stopped by few mm of aluminium
• gamma properties


  weakly ionizing, travels several metres in air, stopped by several cm of lead
• neutron emission is the emission of a neutron from the unstable nucleus of an atom
• alpha decay is when the mass number decreases by 4 and the atomic number decreases by 2
• beta decay is when the atomic number increases by 1
• gamma decay is when both the atomic and mass number stay the same
• the half-life of a radioactive substance is the time taken for the activity to fall to half its original value or the amount of time it takes for the radioactive nuclei to halve
• irradiation is exposing an object to radiation but the object doesn't become radioactive
• contamination is when unwanted radiation ends up on materials which can cause ionizing radiation
• peer reviews is when research is checked by other scientists to ensure it is accurate and reliable
• the natural causes of background radiation are cosmic rays and radioactive rocks
• the man-made causes of background radiation are nuclear accidents and fallout from nuclear weapons
• exposure to radiation can also depend on location and occupation
• a radioactive tracer is a substance that is used to track bodily functions such as internal organs. It is important that the tracer has a short half-life, must not decay, and must be beta or gamma as they are not as strongly ionizing
• radiotherapy is when cancer cells are destroyed using ionizing radiation however healthy cells can also be damaged as a result.
• nuclear fission is a process that occurs randomly or when a neutron is fired at it. this causes 2 daughter nuclei, 2 or 3 neutrons, and energy being released. this can also trigger a chain reaction
• nuclear fission can be controlled when making a nuclear reactor or can be uncontrolled such as nuclear bombs
• nuclear fusion is the fusing of two light nuclei to form a heavier nucleus. some of the mass is converted to energy which is released as radiation. Happens at extremely high temperatures such as stars