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Radioactivity
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Key terms
• Atom• Nucleus• Protons• Neutrons• Ions• Atomic number• Mass number• Radioactive• Radiation• Alpha particle• Beta particle• Gamma particle• Ionising power• Isotope• Half-life• Penetration• Deflection/ deflected
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Radioactivity: industrial applications
What is radiation?
The nuclei of some atoms are unstable. In order to achieve stability they emit radiation.These materials are called radionuclides.They are radioactive.
Radioactivity is a nuclear process – it is not a chemical process. It is not possible to control the rate of radioactive breakdown of a nuclei, it is a random process
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Background radiation
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Atomic structure
Atoms consist of a nucleus and electronsThe nucleus is made up of protons and neutrons
Blockbusters game
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Characteristics of alpha, beta and gamma radiations
There are three types of radiation that can be emitted from a nucleus of an unstable atom.
Alpha (α)and beta (β) are particles of matterGamma (γ) rays are photon of electromagnetic radiation, with a higher frequency than an x-ray.
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Characteristics of alpha, beta (β+ and β–) and gamma radiations
Particle Constituent Charge MassAlpha (α) Helium nucleus
2 protons and 2
neutrons
+2 4
Beta- minus (β-) Electron -1 Negligible
Gamma (γ) Short-wave, high
frequency em wave
0 0
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Particle Ionising Range Speed Affected by
magnetic field?
Alpha (α) Strong –easily pull
electrons off atoms
(10 000 ionisations
per particle)
Slow Yes
Beta- minus (β-) Weakly (100 atoms
per particle)
Fast Yes
Gamma (γ) Very weakly Speed of light No
Gamma radiation spreads out very quickly. Its intensity decreases by the inverse square law.
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Characteristics of alpha, beta (β+ and β–) and gamma radiations
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• The half-life of a radioactive isotope is defined as the time it takes for the number of nuclei of the isotope in a sample to halve or the time it takes for the count rate from a sample containing the isotope to fall to half its initial level.
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Half-life
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