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Atomic Structure - Coggle Diagram
Atomic Structure
Safety
Irradiation: when a substance is exposed to ionising radiation. The substance does not become radioactive, but may be ionised.
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To limit danger from irradiation: limit time around the source, stay as far away as possible, (last resort) lead lined suit
To limit danger from contamination: hazmat suit, gloves
Half life: too long = unsafe, too short = keep changing = expensive
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History of the atom
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Thomson (1904): The spherical atom is positive, with negative electrons scattered. (plum pudding model)
Geiger, Marsden and Rutherford (1911): Most of the alpha particles travelled straight through the gold foil undetected = most of the atom is empty space, Some of the alpha particles were deflected through large angles = suggests that the centre of the atom is positively charged as alpha particles were repelled, A very small number of alpha particles were deflected backwards through angles greater than 90° = suggests that the centre of the atom is much smaller than the rest of the atom as a whole
Bohr (1914): when atoms are heated they let out specific amounts of energy. This means that electrons are orbiting the nucleus at set distances (shells).
Radiation
Radiation occurs to make unstable atoms more stable. Unstable = too much energy or too many particles
Alpha: Mass number decreases by 4 when an alpha particle is emitted. The atomic decreases by two when an alpha particle is released. Charge: 2+. 2 neutrons, 2 protons. Stopped by 1 sheet of paper. Travels a few cm in air. Strongly ionising - easily knock electrons off of any atoms they collide with.
Beta: An electron. When a nucleus has too many neutrons, a neutron can split into a proton and an electron. The electron is emitted from the nucleus. The mass number stays the same. They atomic number increases by 1. Charge: -1. Mass: 1/2000. Stopped by 5mm aluminium. Travels several metres in air. Moderately ionising.
Gamma: Waves of radiation. No charge, no mass. Never stops in air. Multiple metres of lead or concrete stops it. Weakly ionising.
Half life
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The activity of a radioactive source is the number of unstable atoms that decay every second. Measured in Bq.