1. In Pairs.... …write down all you can remember about radiation and radioactivity. What is radiation? What is radioactivity? What’s the difference?

2. Different types of radiation Alpha – α He nucleus emitted Nucleus gets smaller Beta – β (strictly β - ) Neutron decays in to a proton, an electron and an anti-neutrino Gamma –  Energy released as the nucleus rearranges EM Photon

3. Alpha Decay α decay (α is a helium nuclei, 2 protons and 2 neutrons) i.e. Complete this example:

4. Beta Minus Decay β - decay (β - is a high energy electron) e-e- νeνe n p Before After W- The standard formula:

5. Beta Plus Decay β + decay (β + is a high energy positron) e+e+ νeνe n p Before After W+ The standard formula:

6. Gamma Emission No change occurs in the number of protons or neutrons in the nucleus The energy released in gamma ray ( γ ) emission comes from reordering the nucleus to a more stable arrangement It usually occurs after the emission of an α particle or a β - particle

7. Electron Capture A new one for you! This occurs in proton rich nuclei, where the nucleus captures an inner shell electron, causing a proton to turn in to a neutron emitting a neutrino. The inner shell vacancy is filled by an outer shell electron causing the emission of an X-ray photon The standard formula:

8. So that’s radiation, what’s radioactivity? Radioactivity is the decay of unstable isotopes of an element, which results in the emission of ionising radiation. Discuss - Why is something unstable?

9. Consider a nucleus with 14 nucleons... We can arrange the protons and neutrons in different ways... PN P N P N P N P N P N P N PN P N P N P N N P N P N N PN P N P N P N P P N P N P This is stable. There are the same number of protons and neutrons, they are packed in their lowest energy state These are possible but unstable. There are either too many neutrons or too many protons, so they not in their lowest energy state. N N N N N P N This is impossible, far too unstable to exist! N N N N P N N

10. The process of radioactive decay Radioactive decay is dangerous because of the ionising radiation emitted. In addition for a single atom of an isotope, the process is random and uncontrollable. They could decay at any moment...

11. Please listen very carefully!

12. Dice Analogue Draw a table like the one shown. Count you initial number of blocks; enter this as your zero ‘ Dice Remaining’ reading. Roll your blocks, if they land colour side up then they have decayed, put them to one side. Count the number decayed and calculate the number of remaining blocks. Repeat this process making sure you do not lose any blocks. Once you have all your data, enter it on the class spread sheet. Throw Number Dice DecayedDice Remaining 0----------------- 1 2 … 19 20

13. Review the Dice Analogue Experiment 1.Why is this experiment a good analogue for radioactive decay? 2.Will the values ever really reach zero if they were radioactive isotopes? 3.If you replaced the dice with coins how would your results be affected? 4.If radioactive isotopes A decayed faster than radioactive isotope B, which would be more dangerous and why?

14. Radioactivity The decay of any single nucleus is completely random You cannot predict when any one nucleus will decay If there are enough nuclei you can accurately estimate how many nuclei will decay every time period.