topic 4

• john daltons model was in 1804
• rutherford experiment was in 1909
• unstable elements usually decay into other elements and give out radiation as they try to become more stable - this process is called radioactive decay
• radioactive substances spit out 1+ types of ionising radiation from the nucleus
• ionising radiation is radiation that knocks off electrons from atoms
• alpha radiation is when alpha particles are emitted from the nucleus
• alpha particles have 2 neutrons and 2 protons
• alpha particles dont penetrate very far into materials - only a few cm in the air and can be absorbed by a piece of paper
• alpha particles are very ionising becuase of the size
• alpha particles are used in smoke detectors as it ionises the air particles causing a current to flow and if there is smoke in the air it binds to the ion making the current stop causing an alarm
• beta particles are high speed electrons
• beta particles have virtually no mass and a chare of -1
• beta particles are moderately ionising
• beta particles could be absorbed by 5mm thick aluminium
• for every beta particle emitted a neutron in the nucleus has turned into a proton
• beta particles can be used to test thickness of sheets of metal
• gamma rays are electromagnetic waves with a short wavelength
• gamma rays can travel a long way through air and can penetrate a long way without being stopped
• gamma rays are weakly ionising as they pass through things instead f colliding