1. Radioactive Decay What happens to the nucleus of an atom when it emits a radiation? Starter: Think about the reaction between Mg and O  BRIGHT WHITE LIGHT What is happening? Too easy? Think about the particles.

2. MgO Magnesium loses 2 electrons – gives them to oxygen Oxygen therefore gains 2 electrons. ~ a simple example showing that atoms can gain / lose electrons in NORMAL Reactions.

3. Learning Outcomes H: complete equations to show the effect on the nucleus of the emission of alpha or beta particles H: explain what isotopes are.

4. Isotopes Isotopes are atoms of the same element with different mass numbers That is; Same Atomic Number Same no. of protons Different Mass Number Different no. of neutrons

5. IsotopeSymbolPNE Protium 101 Used as fuel, for hardening margarine. Deuterium 111 Used in heavy or deuterated water, solvent Tritium 121 Radioactive, Used in H-bombs, glow in the dark paints Isotopes of hydrogen

6. ProtiumDeuterium Tritium 1 proton, 0 neutron, 1 electron 1 proton, 1 neutron, 1 electron 1 proton, 2 neutron, 1 electron

8. Isotopes ElementSymbolMass NoAtomic NoProtonsNeutronsElectrons Chlorine-35Cl3517 Chlorine-37Cl3717

9. Alpha Decay When an unstable nucleus emits an alpha particle it loses 2 protons and 2 neutrons For example, Radium 226 decays by alpha emission 226 88 Ra 222 86 Rn+ 4 2 He Note: The atomic and mass numbers on both sides of the equation balance.

10. Beta decay – more complex A beta particle is an electron. But where does this electron come from? When an unstable nucleus emits an electron, a neutron in its nucleus changes into a proton and an electron. The electron is emitted. For example Polonium-218 decays by beta emission 218 84 Po 218 85 At + 0 e Note: The atomic and mass numbers on both sides of the equation balance.

11. Gamma Decay After an alpha or beta particle has been emitted from the nucleus of an isotope, the nucleus has too much energy. To get rid of that excess energy, a gamma wave is emitted.

12. Summary Alpha Decay Beta Decay Gamma Decay a wave of energy 226 88 Ra 222 86 Rn+ 4 2 He 218 84 Po 218 85 At + 0 e

13. Task Complete the card sort “decay series”

14. Task: produce a poster showing clearly the types of nuclear decay. C- explain each type of decay B – give chemical examples which show the number of p, n and e before and after decay. A – describe the relative dangers of each type of ionising radiation linking each to what they are made of.

15. Plenary – Block Busters http://www.teachers- direct.co.uk/resources/quiz-busters/quiz- busters-game.aspx?game_id=10700 http://www.teachers- direct.co.uk/resources/quiz-busters/quiz- busters-game.aspx?game_id=10700