_Topic 7_2__Radioactive decay - Topic 7 Atomic and nuclear physics 7.2 Radioactive decay Radioactivity 7.2.1 Describe the phenomenon of natural

_Topic 7_2__Radioactive decay - Topic 7 Atomic and nuclear...

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Radioactivity7.2.1Describe the phenomenon of natural radioactive decay.7.2.2Describe the properties of alpha and beta particles and gamma radiation.7.2.3Describe the ionizing properties of alpha and beta particles and gamma radiation.7.2.4Outline the biological effects of ionizing radiation.7.2.5Explain why some nuclei are stable and others are unstable.Topic 7: Atomic and nuclear physics7.2 Radioactive decay
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RadioactivityDescribe the phenomenon of natural radioactive decay.In 1893, Pierre and Marie Curie announced the discovery of two radioactiveelements, radium and polonium.When these elements were placed by a radio receiver, that receiver picked up some sort of activity coming from the elements.Topic 7: Atomic and nuclear physics7.2 Radioactive decayFYIStudies showed this radioactivi-ty was not affected by normal physical and chemical processes.
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RadioactivityDescribe the phenomenon of natural radioactive decay.In 1896, while studying a uranium compound, French scientist Henri Becquerel discovered that a nearby photographic plate had some- how been exposed to some source of "light" even though it had not been uncovered.Apparently the darkening of the film was caused by some new type of radia- tion being emitted by the uranium com- pound.This radiation had sufficient energy to pass through the cardboard storage box and the glass of the photographic plates.Topic 7: Atomic and nuclear physics7.2 Radioactive decay
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RadioactivityDescribe the properties of alpha and beta particles and gamma radiation. Studies showed that there were three types of radioactive particles.If a radioactive substance is placed in a lead chamber and its emitted particles passed through a magnetic field, as shown, the three different types of radioactivity can be distinguished.Alpha particles () are two protons and two neu- trons. This is identical to a helium nucleus 4He.Beta particles () are electrons that come from the nucleus.Gamma rays () are photons and have no charge.Topic 7: Atomic and nuclear physics7.2 Radioactive decay+20-1heavylight-
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RadioactivityDescribe the properties of alphaand beta particlesand gamma radiation. When a nucleus emits an alpha particle() it loses two protons and two neutrons.All alpha particles have an energy of about 5 MeV.The decay just shown has the form241Am 237Np + 4He.Since the energy needed to knock electrons off of atoms is just about 10 eV, one alpha particle can ionize a lot of atoms.It is just this ionization process that harms living tissue, and is much like burning at the cell level.Topic 7: Atomic and nuclear physics7.2 Radioactive decay
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