radioactivity and particules

• the nucleus of an atom contains protons and neutrons
• the number of protons in the nucleus is called the atomic number
• the total number of protons and neutrons is called mass number
• the protons are negatively charged
• number of protons = number of electrons
• isotopes are elements with the same number of protons but different number of neutrons
• if the isotope has an unstable nucleus, it decays and emits radiation
• the nuclei of unstable isotopes break down at random
• There are four types of radiation, Alpha, Beta, Gamma and neutrons
• ionisation is where an electron is knocked off an atom, the atom with no overall charge turns into an ion with a charge
• alpha particles are helium nuclei
• beta particles are electrons
• gamma rays are very short wavelength EM waves
• alpha particles are made up of 2 protons and 2 neutrons
• alpha particles are big, heavy and slow moving
• alpha particles are blocked by paper, skin or a few cm on air
• alpha particles are stopped quickly
• alpha particles are strongly ionising, they bash into a lot of atoms and knock electrons off
• alpha particles are electrically charged (positively charged) and are deflected by electric and magnetic fields
• alpha particles decrease the atomic number by 2 and mass number by 4
• beta particles increase the atomic number by 1 and mass number stays the same
• beta particles move fast and are small
• beta particles are moderately ionising
• beta particles have a negative charge
• beta particles are stopped by thin metal
• gamma rays have no mass and are just energy
• gamma rays are weakly ionising
• gamma rays have no charge
• gamma rays can be stopped by thick lead or thick concrete
• half life is the time taken for half the radioactive atoms now present to decay
• half life is the time taken for the activity to fall by half
• medical tracers use beta or gamma radiation
• radiation is used to treat cancer
• food and equipment can be sterilised using gamma rays
• radiotherapy kills cancer cells and stops them from dividing
• gamma emitting tracers are used in industry to detect leaks in underground pipes
• ionising radiation can damage cells and tissues
• alpha particles cant penetrate the skin so will do damage if gets inside the body.
• ionisation causes damage and destroys the molecules in the body
• lower doses cause the cell to mutate and divide rapidly, higher doses cause the cell to die