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P4 - Atomic Structure - Coggle Diagram
P4 - Atomic Structure
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L2 - History of the Atom
Democritus - Stated that atoms (atomus) are the smallest, indivisible pieces of matter.
Dalton - Proposed that everything was made of atoms, they were tiny, indivisible spheres.
Thompson - Proposed the plum pudding model, atoms had a neutral charge, within was positive matter and scattered in the atom was negative charges.
Rutherford - Partook in the Rutherford Scattering, proved that all of an atoms mass was concentrated in its centre within a positively charged nucleus. He also proposed that most of an atom was empty space.
Bohr - Bohr first the idea of energy levels, he stated that electrons orbit an atom's nucleus. He proved that electrons gain or lose energy via moving up or down an energy level; absorbing or emitting electromagnetic radiation.
L3 - Types of Radiation
A nucleus emits radiation as it becomes more stable. This process is known as radioactive decay. When a particle is given out in order for the nucleus to become stable, we refer to the nucleus as "decaying".
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Alpha - A cluster of subatomic particles with the same structural make-up as a single helium atom (2 protons, 2 neutrons). This type of radiation is relatively massive in comparison to beta and gamma (inferior penetration properties. so can knock electrons off easily (highly ionising). Stopped with a sheet of paper.
Beta - A single, high energy, high speed electron (negative charge); this electrons is small and light (mediocre penetrative properties) so does not knock off electrons easily (not proficient at ionising). A few mm of aluminium will stop beta radiation.
Gamma - Sometimes when a nucleus emits beta or alpha radiation, it releases some surplus energy also (known as a gamma wave) as the nucleus will have too much energy. Gamma waves have no mass so will not cause ionisation, their penetrating properties are superior to alpha and beta, however. A few cm of lead is likely to stop most gamma radiation but not all.
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L4 - Half life
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Radioactive decay is a random process but with a large enough sample, it is possible to predict how many nuclei in the sample will decay in a certain amount of time.
The more unstable a nucleus is, the shorter its half-life; a lot of radiation is emitted in a short period of time.
L6 - Uses of Radiation
Radioactive tracers - A radioactive, gamma-emitting source will be ingested or injected, the source will collect in certain areas to see if there is an issue in that area. Typically the tracers will gather in very dense area (such as in or around a tumour).
Radiotherapy - A concentrated gamma ray will be emitted, targeting a specific tissue / part of the body (often a tumour), gamma has some ionising capability so it will damage and destroy the DNA of the cell / tissue.
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