iGCSE Physics Section G Radioactivity and particles

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Electrons, protons and neutrons

Neutron: uncharged
Proton: positive charge about the same mass as a neutron
Electron: negative charge but smallest particle.

¹² Atomic mass: number of protons and neutrons
        Atomic number: number of protons
Alpha particles: Helium nuclei. Short range. Heavily ionising
Beta particles: Electrons. Long range. Less ionising.
Gamma rays: Photons. Extremely penetrating.
Alpha and Beta emissions change the atomic number of the original decaying element.
Decaying equations must balance. The sum of the atomic masses before and after the decay must be the same, as does the sum of the atomic numbers.

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Radiation and half-life

You can detect ionising radiation by:
photographic film and The Geiger-Muller tube.

Background radiation:
Earths rocks
Cosmic rays
Medical
Nuclear power and weapons.

The rate of decay is measured in bacquerels (one decay per second)

The half-life of a radioactive isotope t½ is the time taken for half the original number of unstable nuclei to decay.

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Radioactivity

Applications:
Medicine - Radioactive tracers / treat illnesses
Sterilisation - kills bacteria
Non-medical tracers - industrial process tracers
Radioactive dating - to find out how long a material has been dead

Hazards:
can kill living cells
can disrupt genetic material - cell mutation
waste products

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Particles

The rutherford model of the atom
Geiger and Marsden's experiment
(http://www.daviddarling.info/images/Rutherford_gold-foil_experiment.jpg)

The amount of deflection depended on:
The speed of the alpha particles
The nuclear charge
How close the alpha particle gets to the nucleus

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Nuclear fission

Fissile: can be split into lighter elements easily.
The parent nucleus produces two daughter nuclei. This can cause a chain reaction.
(http://www.visionlearning.com/library/modules/mid59/Image/VLObject-785-021205011204.gif)

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