Radioactivity (continued 1)
Aperçu
Deep inside some atoms the nucleus is unstable, and at a moment that no one can predict it suddenly throws out a particle or a burst of radiation and changes into a different element. We cannot say when a single nucleus will decay, yet a large sample decays at a steady, measurable rate captured by its half-life.
In this topic you will learn the nature of alpha, beta and gamma emissions and how each changes the nucleus, write decay equations in nuclide notation, and define and calculate half-life from data and decay curves. You will also see how the choice of radioisotope for smoke alarms, sterilisation, thickness control and cancer treatment depends on its radiation type and half-life.
Objectifs
- Know that radioactive decay is a change in an unstable nucleus that can result in the emission of α-particles or β-particles and/or γ-radiation and know that these changes are spontaneous and random
- State that during α-decay or β-decay, the nucleus changes to that of a different element
- Define the half-life of a particular isotope as the time taken for half the nuclei of that isotope in any sample to decay; recall and use this definition in simple calculations, which might involve information in tables or decay curves (calculations will not include background radiation)
- [Supplement] Know that isotopes of an element may be radioactive due to an excess of neutrons in the nucleus and/or the nucleus being too heavy
- [Supplement] Describe the effect of α-decay, β-decay and γ-emissions on the nucleus, including an increase in stability and a reduction in the number of excess neutrons; the following change in the nucleus occurs during β-emission neutron → proton + electron
- [Supplement] Use decay equations, using nuclide notation, to show the emission of α-particles, β-particles and γ-radiation
- [Supplement] Calculate half-life from data or decay curves from which background radiation has not been subtracted
- [Supplement] Explain how the type of radiation emitted and the half-life of an isotope determine which isotope is used for applications including: (a) h ousehold fire (smoke) alarms (b) irradiating food to kill bacteria (c) sterilisation of equipment using gamma rays (d) measuring and controlling thicknesses of materials with the choice of radiations used linked to penetration and absorption (e) diagnosis and treatment of cancer using gamma rays
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Évaluation de la leçon
Félicitations, vous avez terminé la leçon sur Radioactivity (continued 1). Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.
Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- During alpha decay the nucleon number of a nucleus: A. increases by 4 B. decreases by 4 C. stays the same D. decreases by 2 Answer: B
- In beta decay the proton number of a nucleus: A. decreases by 1 B. increases by 1 C. stays the same D. decreases by 2 Answer: B
- The half-life of a source is the time for its activity to: A. double B. fall to zero C. fall to half D. stay constant Answer: C
- A source has a half-life of 4 hours. After 12 hours the fraction remaining is: A. 1/2 B. 1/4 C. 1/8 D. 1/12 Answer: C
- Which radiation is best for sterilising sealed medical equipment? A. alpha B. beta C. gamma D. infrared Answer: C
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Livres recommandés
Pour aller plus loin, ressources libres
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Section de manuel
Nuclear Forces and Radioactivity
Describe the structure and forces present within the nucleus
"Physics: Nuclear Forces and Radioactivity" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/22-2-nuclear-forces-and-radioactivity. Access for free at https://openstax.org/books/physics/pages/1-introduction
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Section de manuel
Half Life and Radiometric Dating
Explain radioactive half-life and its role in radiometric dating
"Physics: Half Life and Radiometric Dating" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/22-3-half-life-and-radiometric-dating. Access for free at https://openstax.org/books/physics/pages/1-introduction
Publiées par d'autres organisations sous licence libre, créditées comme elles le demandent. Les liens ouvrent leurs sites.
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