BRAINCAKE

Radioactivity

Edexcel GCSE PhysicsTopic 6 of 1546 lessons

Revision notes for Radioactivity in Edexcel Physics (1PH0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. The structure of the atomAn atom has a tiny centre called the nucleus.
  2. The size of atoms and small moleculesAtoms are extremely small.
  3. Isotopes, atomic number and mass numberEvery atom of an element has the same number of protons.
  4. Elements and isotopesThe number of protons in a nucleus decides which element an atom is.
  5. Relative mass and charge of particlesProtons, neutrons, electrons and positrons are compared using relative mass and relative charge.
  6. Why atoms are neutralAn atom has no overall electric charge, so we say it is neutral.
  7. Electron orbits around the nucleusEvery atom has a tiny central nucleus made of protons and neutrons.
  8. Electrons changing orbitAn electron can move from one orbit to another, but only when the atom takes in or gives out electromagnetic radiation.
  9. Forming positive ionsA neutral atom has equal numbers of protons and electrons, so the positive and negative charges cancel.
  10. Types of nuclear radiationSome nuclei are unstable.
  11. Ionising radiationAlpha particles, beta minus particles, positrons and gamma rays are all ionising radiation.
  12. Background radiationBackground radiation is the low level of ionising radiation that is around us all the time.
  13. Origins of background radiationThere is always a small amount of radiation around us, even when no radioactive source is nearby.
  14. Detecting and measuring radioactivityWe cannot see, hear or feel radioactivity, so we need detectors.
  15. Alpha, beta and gamma radiationUnstable nuclei give out three main types of radiation.
  16. Penetration and ionisation of radiationsThe three types of radiation differ in how far they travel through materials, which is their penetration, and in how easily they knock electrons off…
  17. Changes in the atomic modelScientists change a model when new evidence does not fit it.
  18. Beta minus decayIn beta minus decay a neutron in an unstable nucleus changes into a proton and an electron.
  19. Beta-plus decaySome nuclei have too many protons for the number of neutrons they hold.
  20. Changes to atomic number and mass number in decayThe atomic number is the number of protons in a nucleus.
  21. Gamma emission after decayAfter an alpha or beta decay, the new nucleus is often left with extra energy.
  22. Balancing nuclear equationsIn a nuclear equation, the nucleus before the decay is on the left and the products are on the right.
  23. How activity decreases over timeThe activity of a radioactive source is the number of nuclei that decay each second.
  24. The becquerelThe activity of a radioactive source is the number of nuclei that decay each second.
  25. Half-lifeAn unstable nucleus decays at random, and the activity of a radioactive source gradually falls as more of its nuclei decay.
  26. Random decay and half-lifeRadioactive decay is random.
  27. Half-life calculationsTo carry out a half-life calculation, first work out how many half-lives have passed by dividing the total time by the half-life.
  28. Uses of radioactivityRadioactive sources are useful because their radiation is easy to detect and can kill living cells.
  29. Dangers of ionising radiationIonising radiation includes alpha, beta and gamma radiation and x-rays.
  30. Dangers of radiation and half-lifeIonising radiation can damage or kill living cells, and it can cause mutations in DNA that may lead to cancer.
  31. Radiation safety precautionsPeople who work with radiation must be protected, because ionising radiation can damage cells.
  32. Contamination and irradiationIrradiation happens when an object or person is exposed to radiation from a source that is outside it.
  33. Treating tumours with radiation, inside or outside the bodyRadiation can kill the cells of a tumour.
  34. Radioactive tracers and PET scanners in diagnosisRadioactive substances can help doctors see how the body is working without cutting it open.
  35. Why PET isotopes must be made nearbyThe isotopes used in PET scanners have very short half-lives.
  36. Evaluating nuclear power for generating electricityNuclear power stations use the energy from fission of uranium or plutonium to make electricity.
  37. Nuclear reactions as an energy sourceEnergy is released when the nucleus of an atom changes.
  38. Fission of uranium-235Uranium-235 is the fuel used in most nuclear reactors.
  39. The principle of a chain reactionEach fission of uranium-235 releases two or three neutrons.
  40. Controlling a nuclear reactorInside a reactor, fuel rods containing uranium-235 are surrounded by a material that slows neutrons down and are interspersed with rods that absorb…
  41. Electricity from nuclear fissionA nuclear power station is a thermal power station.
  42. Radioactive products of fissionWhen a uranium-235 nucleus splits, the two daughter nuclei are not usually stable.
  43. Nuclear fusion and starsNuclear fusion is the joining of small nuclei to make a larger nucleus.
  44. Fusion compared with fissionBoth fusion and fission are nuclear reactions that release energy, and in both the products have slightly less mass than the starting nuclei.
  45. Why fusion needs high temperaturesNuclei are made of protons and neutrons, so every nucleus has a positive charge.
  46. Fusion power stationsFusion would be an attractive source of electricity.

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