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Structure of an atom
· Nucleus ­ middle of atom contains neutrons (no charge)
and protons (positive charge +1).
· Almost all of the mass is in the centre of an atom however,
size wise, it is tiny compared to the rest of the atom.
· Around the nucleus are electrons (negatively charged -1).
· They have virtually no mass and occupy shells around the
· Most of an atom if empty space ­ Rutherford's
· You should know most of this from chemistry and earlier
years, make sure you know what is the atomic number,
mass number, and what isotopes are too.…read more

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Emitting radiation
· If an atom emits radiation, it does so to
become more stable.
· The radiation originates from the nucleus
of the atom.…read more

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Rutherford's investigation
Rutherford and his team of scientists tried an experiment with a thin sheet of
gold foil and an alpha particle laser beam. This experiment lead to the model of
the atom that we now associate as the nuclear atom.
Observations that were made:
1. Atoms are mostly of empty
space so most alpha particles
went straight through the foil.
2. The nucleus is very small
compared to the size of the
atom and it contains most of the
mass and all the positive charge,
hence some alpha particles were
deflected through large angles,
and very few particles were
reflected straight back.…read more

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Background radiation
· Background radiation is radiation that occurs
naturally all around us. It only provides a very
small dose altogether so there's no danger to
our health.
· 13% come from
man made sources
· 87% come from
natural sources…read more

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Alpha decay
· Emits alpha particle (helium nuclei)
· 2 neutrons and 2 protons are emitted from
the nucleus
· (sign of alpha)
· When the unstable atom has emitted an alpha
particle, it's mass number becomes 4 less,
whilst it's atomic number becomes 2 less.
· E.g. 238
92 U 92 Th + 2 + energy
238 4…read more

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