atomic structure

• alpha particles emit 2 neutrons and 2 protons so mass number increases by 4 and atomic number decreases by 2
• when an atom has too few neutrons, it will emit an alpha particle to balance everything
• when an atom has too many neutrons it will emit a fast-moving electron from the nucleus known as a beta particle
• beta particles cause the atomic number to increase and the mass number to stay the same
• alpha has a +2 charge, is highly ionising and has low penetration power - can be stopped by paper
• beta has a -1 charge, is weakly ionising and can be stopped by aluminium
• gamma has 0 charge, very weakly ionising but high penetration power and is only stopped by lead
• gamma emits infrared radiation in the form of a electromagnetic wave to cool the atom down
• half-life is the time taken for the number of radioactive nuclei in the sample to halve
• irradiation is exposing an object to nuclear radiation without the object becoming radioactive
• irradiation is used to sterilise fruit and medical equipment as it can damage living cells but can be harmful and may not kill all bacteria
• contamination is the unwanted presence of materials containing radioactive atoms
• contamination can be used as tracers in medical imaging but they may be left behind, not go where you want or damage healthy cells
• a short half-life is only dangerous for a small time as it emits a high amount of radiation at the start but quickly becomes safe
• radiation is measured using a geiger-muller tube which records the count rate and is measured in becquerels