4451609
Description
Flashcards by Will Welford, updated more than 1 year ago
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Created by Will Welford
about 8 years ago
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| Question | Answer |
| Conclusions from the Rutherford scatttering | 1. Atom is made up mostly of empty space --> alpha particles passed straight through 2. Nucleus must have a large positive charge --> alpha particles repelled/ deflected at large angles. 3. nucleus is very small 4. mass is concentrated in the nucleus. |
| nuclear decay | The process by which an unstable nuclei releases energy/ particles to become more stable. |
| Alpha radiation | 1. 2 protons + 2 neutrons 2. absorbed by paper/ skin/ few mm of air 3. very strongly ionising 4. deflected in magnetic fields. |
| decay by alpha | nucleon number decreases by 4 proton number decreases by 2 |
| Alpha uses | Because it is very ionising, it allow a current to flow in smoke alarms. When smoke is present, current no longer flows, leading to alarm |
| Beta - radiation | 1. fast moving electron 2. stopped by a few cm of aluminium 3. medium ionising 4. deflected in magnetic fields |
| decay by beta | neutron turns into a proton proton number increases by 1 release of an anti-neutrino |
| beta uses | controlling paper thickness |
| Beta + | 1. made up of a positron 2. almost immediately annihilates with electrons, so have 0 range |
| beta + decay | proton turns into a neutron proton number decreases by 1 release of a neutrino |
| gamma | 1. EM wave 2. absorbed by many cm of lead 3. weakly ionising due to no mass 4. passes straight through magnetic fields due to no charge 5. Emitted due to daughter nucleus being in an excited state, which then de-excites, emitting gamma and becoming more stable. |
| gamma decay | proton and neutron numbers remain the same |
| gamma uses | medical tracers treatment of cancer |
| Why should it not have a short half-life? | So activity does not fall too low too quicky |
| why should it not have a long half-life? | to avoid damage long-term damage to the body |
| electron capture | 1. nucleus captures and absorbs an orbiting electron 2. proton changes into neutron 3. neutrino is released |
| safe handling of radioactive sources | 1. hold source as far away from body as possible (using long handling tongs). Due to gamma inverse square law and limited range of alpha and beta, this limits the amount of radiation that hits you. 2. store in a lead-lined container 3. should only be used for as long as necessary. |
| isotopes | elements with the same number of protons but different number of electrons |
| decay constant | probability of a specific nucleus decaying per unit time. |
| Activity | The number of nuclei that decay per second |
| Half-life | The average time it takes for the number of unstable nuclei to decay by half |
| mass defect | mass of the nucleus is less than the mas of its constituent nucleons |
| binding energy | The energy required to separate a nucleus into its constituent nucleons |
| nuclear fission | When large unstable nuclei randomly split to form two smaller nuclei |
| nuclear fusion | When two light nuclei combine to create a larger nucleus. |
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