Do now!

1. Do now! Can you write the title P15 Radioactivity in your books?

2. Radioactivity

3. Today’s lesson • Demonstrate understanding of background radiation. • Describe the detection of α-particles, β-particles and γ-rays. • State that radioactive emissions occur randomly over space and time. • State the meaning of radioactive decay. • Describe the hazards of ionising radiation to living things. • Describe how radioactive materials are handled, used and stored in a safe way to minimise the effects of these hazards. • Use the term isotope.

4. The atom orbiting electrons Nucleus (protons and neutrons)

5. Nuclide notation Atomic mass (mass number) = number of protons and neutrons orbiting electrons 7 Li 3 Atomic number (proton number) = number of protons Nucleus (protons and neutrons)

6. 7 6 Li Li 3 3 Isotopes It is possible for the nuclei of the same element to have different numbers of neutrons in the nucleus (but it must have the same number of protons) 3 neutrons 4 neutrons

7. Relative atomic mass On average, lithium atoms have a mass of 6.941 (relative to Carbon 12) 6.941 Li 3

8. 1 2 3 H H H 1 1 1 Isotopes of Hydrogen The three isotopes of Hydrogen even have their own names! Hola! Mi nombre es tritium y yo soy de Madrid! They call me deuterium Hi! I’m hydrogen

9. Questions p251

10. Unstable nuclei Some nuclei are unstable, for example Uranium 235 Hi! I’m uranium-235 and I’m unstable. I really need to lose some particles from my nucleus to become more stable.

11. Unstable nuclei To become stable, an unstable nuclei emits a particle. We say the atom has decayed

12. Unstable nuclei The decay of an unstable nucleus is random. We know it’s going to happen, but we can’t say when! It cannot be affected by temperature/pressure etc. Weeeeeeeeeeeeee!

13. Detection • Particles can be detected by photographic film • Particles can also be detected (and counted) by a Geiger-Müller tube (GM tube) connected to a counter

14. Background radiation There are small amounts radioactive particles around us all the time. This is called background radioactivity. The amount varies depending on location.

15. Background radiation COPY PLEASE Background radiation comes from • Cosmic rays from space • Radioactive rocks in the ground • Nuclear tests • Nuclear bombs • Nuclear accidents

16. Hazards of ionising radiation

17. Ionising • The radioactive particles (more about later) can ionise atoms they collide with

18. Hazards of ionising radiation • Ionizing radiation has the ability to break chemical bonds and facilitate exotic chemical reactions within living cells. The damage caused to cells can vary; • radiation burns • hair loss (temporary or permanent) • cancer • reproductive sterility • mutations in offspring

19. Radiation Safety

20. Radiation Safety Get away dog! • Run away! Mr Porter a few years ago

21. Radiation Safety • Run away! • In other words keep the distance between you and a radioactive source as big as possible!

22. Radiation Safety • Don’t waste time!

23. Radiation Safety • Don’t waste time! • In other words limit the time you are exposed to radiation.

24. Radiation Safety • If you can’t run away, hide behind something!

25. Radiation Safety • If you can’t run away, hide behind something! • Put a barrier between you and the radiation source that can absorb the radioactive particles

26. Radiation safety • Keep the distance between you and a radioactive source as big as possible (use tongs etc.) • Limit the time you are exposed to radiation. • Put a barrier between you and the radiation source that can absorb the radioactive particles (normally lead)

27. Let’s try some questions. Let’s do some reading. Page 250 onwards.