1. Using the pie chart below, write a paragraph,
Prepare to Learn
Using the pie chart below, write a paragraph,
summarising the main sources of background radiation.

2. Stable and Unstable Nuclei
Text books
Stable and Unstable Nuclei
Homework: Read pages 4 & 5
Makes notes on the section ‘specific charge’

3. Objectives
To know what keeps protons and neutrons together in the nucleus (knowledge)
To understand why some nuclei are unstable (knowledge & application)
To be able to complete decay equations for alpha and beta decay (analysis)

4. Recap from KS4

5. Present new information
The strong nuclear force

6. Radioactive Decay

7. Present New Information
Select 20 elements off the periodic table
Record the number of protons (z) and the number of neutrons (N) in a table (you will need to make sure one of you elements has a proton number of 90+)
Plot a graph of N against z and draw a line of best fit
Label this line ‘line of stability’
Add a dotted line to your graph for N=z

8. Construct – Using the Graph
Task 1
Area to the right of z = 84
Shade in blue
This area represents elements that are all unstable.
They decay by a decay – label the area ‘alpha decay’
Task 2
Colour the section above the line of stability red
In this region, the nuclei are ‘neutron rich’
They decay by electron emission
This is beta-minus decay
Task 3
Colour the section below the line of stability green
In this region, the nuclei are ‘proton rich’
They decay by positron emission
This is beta-plus decay

9. Beta minus a neutron in an atom's nucleus turns into a proton
Mini-review
Alpha emitters
Beta plus a proton in an atom's nucleus turns into a neutron

10. Alpha Decay

11. Copy the equation and label the:
Parent nucleus
Daughter nucleus
Alpha particle

12. Mini Review Write the alpha decay equation for Polonium (208, 84)

13. What happens in beta-minus decay
Some new particles here, but don’t worry too much – we do a separate lesson on antimatter in a few weeks!

14. What is the actual process?
The isotope has too many neutrons
A neutron changes into a proton + an electron (b-)
This requires a down quark to change into an up

15. Copy the equation
Label – parent nucleus, daughter nucleus, beta minus, anti-electron neutrino and energy
Write the decay equations for a beta-minus decay from:
Carbon (14,6)
Oxygen (19,8)

16. Compare with beta-minus

17. Mini Review Write a general equation for beta plus decay
Add the energy
Label each section of the equation

18. What actually happens? The isotope has too many protons
A proton changes into a neutron + a positron (b+)
This requires an up quark to change into a down quark
Write a beta-plus decay equation for Oxygen (15-8)

19. Mini Review
Alpha Decay
Beta Decay

20. Apply to demonstrate
In the actinium series, uranium-235 (235,92) decays by the emission of 5 alpha particles and two beta-minus particles.
Determine the proton and nucleon number of the nuclide formed when these decays have taken place.

21. Summary Stable nuclides
Heavier nuclides have more neutrons than protons
Most nuclides have an even no. of p and n
Implies alpha is a stable combination
O, Si and Fe account for over 75% of earth’s crust
Unstable nuclides
Disintegrations tend to produce new nuclides nearer the stability line
A nuclide above the line decays to increase proton number i.e by β emission
A nuclide below the line disintegrates so that Z decreases

22. Review of Objectives
To know what keeps protons and neutrons together in the nucleus (knowledge)
To understand why some nuclei are unstable (knowledge & application)
To be able to complete decay equations for alpha and beta decay (analysis)