radioactivity
TRANSCRIPT
Radioactivity
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
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
Background radiation
Atomic structure
Atoms consist of a nucleus and electronsThe nucleus is made up of protons and neutrons
Blockbusters game
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.
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
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.
Characteristics of alpha, beta (β+ and β–) and gamma radiations
• 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.
Half-life