Do now!

1. Do now! Can you look through your books and read the comments? Can you also look through the tests and make sure that Mr Porter has added the marks up correctly?

2. Today’s lesson • Recall for radioactive emissions; • their nature, • their relative ionising effects, • their relative penetrating abilities. • Describe the deflection of α-particles, β-particles and γ-rays in electric fields and magnetic fields. • Interpret their relative ionising effects. • Use equations (involving words or symbols) to represent changes in the composition of the nucleus when particles are emitted.

3. 3 types of particle You’ll learn about some really weird ones in year 13! There are 3 (at least in IGCSE!) types of particles that can be ejected from an unstable nuclei.

4. Alpha particles Hi! α

5. Alpha particles • 2 protons and 2 neutrons joined together • The same as the nucleus of a helium atom • Stopped by paper or a few cm of air • Highly ionising • Deflected by electric and strong magnetic fields 2+ 4 He 2

6. 235 231 U Th 92 90 Alpha Decay Atomic mass goes down by 4 α + Atomic number goes down by 2

7. Beta particles Yo! β

8. Beta particles • Fast moving electrons • Stopped by about 3 mm of aluminium • Weakly ionising • Deflected by electric and magnetic fields e 0 -1

9. 231 231 Th Pa 90 91 Beta decay • In the nucleus a neutron changes into an electron (the beta particle which is ejected) and a proton (which stays in the nucleus) • During beta decay the mass number stays the same but the proton number goes up by 1. e 0 + -1

10. Gamma rays Hola!

11. Gamma rays • High frequency electromagnetic radiation • Stopped by several cm of lead • Very weakly ionising • NOT affected by electric or magnetic fields

12. 235 231 U Th 92 90 Gamma rays Associated with alpha decay α +

13. Penetration

14. Deflection by electric fields

15. Deflection by magnetic fields

16. Summary – stick in!

17. Questions! • Page 253