1. Calculate the “theoretical” mass of an alpha particle, using: Proton mass = 1.67338 x 10 -27 kg Proton mass = 1.67338 x 10 -27 kg Neutron mass = 1.67483 x 10 -27 kg Neutron mass = 1.67483 x 10 -27 kg 2p + 2n = 6.69642 x 10 -27 kg 2p + 2n = 6.69642 x 10 -27 kg Do now: Paraire, 16 Whiringa-ā-nuku 2015 The actual mass of an alpha particle has been measured to be 6.64591 x 10 -27 kg What’s going on??? What’s going on???

2. Explain this “mass deficit” in terms of nuclear binding energy Explain this “mass deficit” in terms of nuclear binding energy Use the concept of binding energy per nucleon to explain the stability of nuclei Use the concept of binding energy per nucleon to explain the stability of nuclei Today’s Learning: I’m away on Wed: so time for you to complete Activity 12A and 12B I’m away on Wed: so time for you to complete Activity 12A and 12B H/W Set 3 due next Mon 25 th March H/W Set 3 due next Mon 25 th March Notices:

3. I’m away on Wed: so time for you to complete Activity 12A and 12B I’m away on Wed: so time for you to complete Activity 12A and 12B H/W Set 3 due next Mon 25 th March H/W Set 3 due next Mon 25 th March Waves test: re-sit Thursday lunchtime (S2) Waves test: re-sit Thursday lunchtime (S2) - compulsory for anyone who scored “N” - compulsory for anyone who scored “N” - recommended for anyone who scored < 12/24 - recommended for anyone who scored < 12/24 Notices:

4. Binding Energy Mass number 50 100150 200 Binding energy per nucleon (MeV) 2 4 6 8 56 Fe 238 U 4 He 7 Li Fusion Fission