1. Don’t forget you have a test on Thursday!
Do now!
Don’t forget you have a test on Thursday!
Can you write the title
Radioactivity
in your books?

2. Radioactivity

3. Today’s lesson
describe the structure of an atom in terms of protons, neutrons and electrons and use symbols to describe particular nuclei
understand the terms atomic (proton) number, mass (nucleon) number and isotope
understand that ionising radiations can be detected using a photographic film or a Geiger-Muller detector
recall the sources of background radiation

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

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

6. 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) Li 3 7 Li 3 6

7. Isotopes
For example, Lithium atoms occur in two forms, Lithium-6 and Lithium-7
3 neutrons
4 neutrons Li 3 7 Li 3 6

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

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

10. Questions! Element Chemical symbol Atomic number Hydrogen H 1 Helium2
Lithium Li 3
Beryllium Be 4
Boron B 5
Carbon C 6
Nitrogen N 7
Oxygen O 8
Radium Ra 88
Thorium Th 90
Uranium U 92
Plutonium Pu 94

11. 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.

12. Unstable nuclei To become stable, an unstable nuclei emits a particle
Weeeeeeeeeeeeee!

13. Unstable nuclei
We say the atom has decayed
Weeeeeeeeeeeeee!

14. 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!

15. Becquerels (Bq)
The amount of radioactivity given out by a substance is measured in Becquerels. One becquerel is one particle emitted per second.

16. 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

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

18. Background radiation Background radiation comes from
Cosmic rays from space
Radioactive rocks in the ground
Nuclear tests
Nuclear bombs
Nuclear accidents

19. Radiation Safety

20. Radiation Safety
Run away!
Mr Porter

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

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. Let’s try some questions.