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P4 - ATOMIC STRUCTURE - Coggle Diagram
P4 - ATOMIC STRUCTURE
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History of the atom
Thompson - Plum pudding model, positive,sphere atoms, negatively charged electrons scattered throughout, neutral altogether 
Geiger, Marsden, Rutherford - directed a beam of alpha particles at a very thin gold leaf suspended in a vacuum (any deflection of the alpha particles would only be because of collisions with gold foil, not due to collisions with air particles.) most alpha particles passed straight through,most of the atom is empty space, some deflected through large angles, center of atom is + charged, positive alpha particles were being repelled by positive charges, a very small number of alpha particles came straight back off the foil center is much smaller than the rest of the atom
Dalton - "All matter is made of atoms", "Atoms are solid spheres that cannot be broken down"
Bohr - When atoms are heated they give off specific amount of energy, electrons orbit the nucleus at set distances (shells)
Half-life
half-life: average time (radiation is random) it takes for the number of radioactive nuclei in a sample to halve
Radiation occurs to make unstable atoms more stable, unstable isotopes= too much energy/ too many particles
Radioactive decay - nuclei with too many, or too few, neutrons do exist naturally but are unstable and will disintegrate (or decay) by emitting radiation.
Safety
Irradiation - when a substance is exposed to ionising radiation, substance does not become radioactive but may be ionised
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How to limit irradiation: wear lead-lined suits, stand a far distance away, limit amount of exposure (time)
Alpha, beta and
gamma radiation (properties)
alpha - 2 protons, 2 neutrons (2+), mass=4 relatively large, penetrates a few cm in air, stopped by a piece of paper, strongly ionising - can knock any electrons off any atoms they collide with
beta - high speed electron emitted by radioactive substances (-1), mass=1/200, penetrates moderately far - several m in the air, stopped by 5mm of aluminium, moderately ionising
gamma - waves of electromagnetic radiation (0), mass=0, penertstres through long distances, stopped by multiple m of concrete/lead, weakly ionising