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P6 ­ Radioactive Materials
Radioactivity
Atoms

Atoms consist of a nucleus and orbiting electrons. The nucleus of an atom
contains protons and neutrons. It makes up most of the mass of the atom,
but takes up virtually no space.

The electrons that orbit the atom are really small. They whizz…

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Beta particles move quite fast and they are quite small. They penetrate moderately into materials
before they are stopped. Beta particles are released by nuclei that have too many neutrons.

During beta decay, a neutron in the nucleus turns into a proton, so the element
changes, and a beta particle…

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Ernest Rutherford

In 1909, Ernest Rutherford, Hans Geiger and Ernest Marsden tried firing positively charged alpha
particles at thin foil. Most of these particles just went straight through but the odd one came straight
back at them.

This meant:

Most of the mass of a gold atom was concentrated at…

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Nuclear reactions release a lot more energy than chemical reactions. Splitting a gram of uranium
releases over 10,000times more energy than burning a gram of oil. You can calculate just how much
energy is released by using E = mc2.

Nuclear Power Stations

In nuclear reactors, a chain reaction is…

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Danger from Radiation
Alpha, beta and gamma radiation are all ionising radiation ­ they can break up molecules into smaller
bits of ions. Ions can be very chemically reactive, so they go off and react with thing and generally
make nuisances of themselves.

In humans, ionisation can cause serious damage…

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Radioactive sources are considered to be safe when the radiation they are emitting is at about the
same level as the background radiation. The half-life of the source gives an idea of how long it will
take for this to happen.

Ionising Radiation

Ionising radiation can be useful for...

Treating…

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