1. Radiation True or False?
You are being bombarded with radiation right now.
You are giving off radiation right now
Your breakfast was irradiated with deadly radiation
You can see radioactivity
You can feel radioactivity
Radioactive substances are only harmful if you touch them
If you are irradiated then you become radioactive
Radioactivity is not very useful
We completely understand what causes radioactivity
Do you know the three types of radioactivity. Write them down..
True
True
True ??
False
False
False
False
False
False ?

2. PM S5 K1: Distinguish between stable and radioactive isotopes and describe the conditions under which the nucleus is unstable.

3. ? Alpha radiation -  Helium nuclei Description:
2 neutrons, 2 protons (helium nuclei)
Electric Charge: +2
Relative Atomic Mass: 4
Penetration power:
Stopped by paper or a few cm of air
Ionisation effect:
Strongly ionising
Effects of Magnetic/Electric Field:
Weakly deflected
Helium nuclei ?

4. Beta radiation -  high energy electron Description:
Electric Charge: -1
Relative Atomic Mass:
1/1860th
Penetration power:
Stopped by few mm of aluminium
Ionisation effect:
Weakly ionising
Effects of Magnetic/Electric Field:
Strongly deflected
high energy electron

5. Gamma radiation -  Electromagnetic radiation Description:
High energy electromagnetic radiation
Electric Charge:
Relative Atomic Mass:
Penetration power:
Reduced by several cms of lead or several metres of concrete
Ionisation effect:
Very weakly ionising
Effects of Magnetic/Electric Field:
NO deflection
Electromagnetic radiation

6. Let’s have a look at some radioisotopes.
Think about how we may be able to use them!

7. The penetration power of the three types of radiation.  
Skin or paper
stops ALPHA
Thin aluminium
stops BETA
Thick lead
reduces GAMMA
Thin mica

8. So what exactly does cause this radiation? .
First we need to look at the structure of the atom

9. Draw diagrams to represent:

10. How did you go? 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons

11. What do we call these? 6 protons 6 neutrons 6 electrons 6 protons

12. Isotopes
Atoms of the same element with different numbers of neutrons

13. Isotopes Atoms of the same element with different numbers of neutrons
Because they have the same number of electrons there is NO difference to their chemical behaviour.

14. Stable and unstable Isotopes
There are over 2000 different isotopes that have been discovered so far.
Only 279 are stable – they do not emit radiation.
The rest are unstable and are called radioisotopes
The nuclei rearrange to become more stable.
As they do so they emit radiation.
But which ones are unstable?
Lets have a look at some of these isotopes.

15. Stable and unstable Isotopes
So why are some nuclei unstable?
Some nuclei are unstable because of the proton to neutron ratio.
For light elements, stable nuclei have a proton:neutron ration close to 1:1.
For heavy elements the stable nuclei have a proton:neutro ratio close to 1:1.5

16. Stable and unstable Isotopes
p = n

17. Uses of radiation

18. Thickness Control Mill
If not enough radioactivity is detected then the rollers compress to make the material thinner.
This method is used in the manufacture of lots of sheet materials: plastics, paper, sheet steel.
A radioactive source is on one side of the material and a detector on the other.
If too much radioactivity is getting through, then the material is too thin and the rollers open up a bit to make the material thicker.
Beta Source
detector
Hydraulic
ram
Electronic instructions to adjust rollers.

19. Leak detection in pipes
The radioactive isotope is injected into the pipe. Then the outside of the pipe is checked with a Geiger-Muller detector, to find areas of high radioactivity. These are the points where the pipe is leaking. This is useful for underground pipes that are hard to get near.
GM tube
The isotope must have a short half life so the material does not become a long term problem.
The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth.

20. Cobalt-60 Sterilisation
Gamma rays are used to kill bacteria, mould and insects in ood. Also used to kill bacteria on hospital equipment.
This is useful particularly on packaged food or on plastic items which would be damaged by heat sterilisation.
It can affect the taste and the vitamin content, but it lengthens the shelf life.
Gamma Source
unsterilised
sterilised

21. Sterilisation Gamma Source unsterilised sterilised
Cobalt-60 is used as it is a gamma emitter – very penetrating.
It has a half life of 5.3 years so the machines can run cheaply without regular maintenance.
You don’t need external power to produce the gamma rays as you do with x-rays
Cobalt-60 is held in a chemically inert form in a sealed container.
When the cobalt-60 is exhausted it can easily be replaced.
Gamma Source
unsterilised
sterilised

22. Radioactive half-life
The average time taken for half of the substance to decay is called the radioactive half-life.

23. What is the half life of Carbon-15?
Radioactive half-life
What is the half life of Carbon-15?

24. PM S5 K5 – Identify one use of a named radioisotope:
in industry
In medicine
PM S5 K6 – Describe the way in which the above named industrial and medical isotopes are used and explain their use in terms of their chemical properties.
(This is your homework – ask for a handout!
Include something about half life in your answers.)
Start by reading p
Cobalt-60 and Technetium 99 are easy to research but it is entirely up to you.

25. Think about this!
What happens if radiation is incident upon a living cell?
Radiation can ionise cells which causes cellular damage.
If the exposure is high, it can kill the cell.
If the exposure is lower it can cause cancer.
The higher the exposure, the higher the risk of cancer.

26. PM S5 P6 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in industries and medicine
Read p98 and from what you have learnt today make a list of benefits.
Read p 101 and from what you have learnt today make a list of problems.

27. Sensitive monitoring of inductrial processes
PM S5 P6 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in identified industries and machines.
Benefits:
Non-invasive diagnostic procedures
Treatement of cancers
Sensitive monitoring of inductrial processes
Sterilisation
Non-invasive examination of pipes / aircraft etc.
Problems:
Tissue damage for people exposed
Risk of cancer if exposed
Genetic damages to people exposed
Hard to dispose of some isotopes (long half-life)