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How can electrons change energy level Absorbing or emitting radiation
What is the atomic number Number of protons
What is the mass number No of protons + no of neutrons
What is an isotope An element with a different number of neutrons
Describe the development of the atom -First atoms were thought to be solid spheres which couldn't be divided -plum pudding model -alpha particle scattering experiment proved that there was a positive nucleus with electrons orbiting is shells James Chadwick proved the existence of neutrons
Describe the alpha particle scattering experiment -alpha particles fired at gold foil -most went straight through -some deflected at angles -only a few bounced off
Define activity The rate at which a source of unstable nuclei decays
Define count rate Number of radioactive counts per second
What are the 4 types of nuclear decay -alpha -beta -gamma -neutron
Describe alpha radiation -helium nucleus -stopped by a peice of paper -strongly ionising
Describe beta radiation -high speed electron -moderatly ionising -absorbed by aluminium
Describe gamma radiation -electromagnetic wave -weakly ionising -absorbed by thick lead
Define half-life The time it takes for the number of radioactive nuclei in a sample to half
Define contamination The presence of radioactive atoms on other materials
Define irradiation Exposure of an object to radiation
Give 2 examples of natural sources of background radiation -cosmic rays -rocks
Give 2 examples of man made sources of background radiation -nuclear accidents -fallout of nuclear weapons testing
What affects a person's level of radiation -job -location
What is radiotherapy High ionising radiation directed at cancer cells to kill them
What are the risks of using radiation -tissue damage -cancers -radiation sickness
Describe the process of nuclear fission -radiation nucleus hit by neutron -neutralises absorbed -nucleus splits into two lighter nuclei -neutralises and energy released -neutralises can cause a chain reaction
Describe the process of nuclear fusion Two light nuclei collide and fuse to form larger nucleus this releases energy
Created by: Liam P