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Radio Activity and Particles
Atoms and Radioactivity:-
Atoms are made up of Electrons, Protons and Neutrons.
Protons and Neutrons make up a very small nucleus.
The Electrons move around the nucleus.
Protons and Neutrons are also called Nucleons ­ they are formed in the nucleus.
Protons and Neutrons are heavier than electrons.
Neutrons are not charged.…read more

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In the air:
Natural radioactivity in the air is due to radon and thoron (radioactive gases).
Gases given off from rocks and soil and can become concentrated inside buildings.
Outside they are dispersed in the air.
The Earth's crust:
All materials in the Earth's crust contain some radioactive isotopes, particularly igneous rocks.
Buildings are radioactive because they are made from materials extracted from the Earth.
Radiation doses in rocks and soil vary considerably over the country as the geology varies.…read more

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Detecting Ionising Radiation =
Henri Becquerel ­ Unit named after him (the Becquerel) 1 Bq- per second
Radiation can be detected using photography film or a Geiger counter.
Glass tube with electric conducting coating on inside.
Tube thin window made of micra (naturally occurring mineral can be split into thin sheets).
Tube contains mixture of gases at low pressure.
In middle of tube, electrically insulated from conducting coating, is an electrode.…read more

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Alpha Strong Weak 5-8cm Paper
Beta Medium Medium 500-1000cm 5mm of Al
Gamma Weak Strong Virtually infinite Thick Pb
Nuclear Transformations:-
Alpha Decay = nucleus loses an alpha particle it becomes a different element
* Ra Rn +
* Rn Po +
Beta Decay = In the nucleus a neutron changes into a proton and an electron. Proton remains in
nucleus but the electron is ejected as a beta particle. New nucleus has the same mass number but the
atomic number by 1.…read more

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An isotope with a half-life of 6 hours has an activity of 8000KBq and a mass of 248g.
a) What will the activity be after 30 hours?
b) What mass will remain after 3 half-lives?
Mass = 248g
Activity = 8000Bq
Half-life = 6 hours
Number of Time elapsed Fraction Mass remaining Activity/count
half-lives (hour) remaining (g) rate (KBq)
0 0 All 248 8000
1 6 ½ 124 4000
2 12 ¼ 62 2000
3 18 1/8 31 1000
4 24 1/16 15.…read more

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Keep sources at a distance
Use lead shielding
Models of the Atom:-
Electron was first atomic particle discovered (JJ Thomson in
1897)
Electron has negative charge and Thomson suggested that an
atom must also contain positive charge to make it electrically
neutral
Model was a sphere of positively charged material with
electrons dotted around within it and this became known as
the "plum pudding"
After this discovery of alpha particles Rutherford used them to investigate the structure of the atom.…read more

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The amount of deflection depends on these factors:
The speed of the alpha particle ­ they deflect less when travelling faster.
The charge on the nucleus ­ the greater the positive charge on the nucleus, the more
strongly the alpha particle will be repelled from it.
How close the alpha particle gets to the nucleus ­ closer to the nucleus, the more deflected.…read more

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If more than one neutron causes further fission then the reaction will get bigger and may get out of
control - resulting in a nuclear explosion.
Nuclear Power:-
Nuclear reactor in a controlled chain reaction takes place and energy is released at a steady
rate.…read more

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Steam turns the turbines which spin the generation to produce electricity
Advantages of Nuclear Power:-
Fission process itself does not produce CO2 or gases that cause acid rain
Only needs small amount of Uranium to produce same amount as tonnes of fossil fuels
Efficient, costs about the same as electricity from fossil fuels
Disadvantages of Nuclear Power:-
NUCLEAR WASTE ­ Spent fuel is very hot and must first be cooled down, tanks of water are
used ­ cooling ponds
Fission process in a nuclear reactor…read more

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