1. 1.3 Learning Outcomes define radioactivity
describe the nature and penetrating ability of alpha, beta and gamma radiation
give one example each of the following: an α emitter, a β emitter and a γ-emitter
explain how radiation is detected having seen a demonstration / video

2. Learning Outcomes define radioisotopes define and explain half life
define and explain half life
give a historical outline of:
Becquerel’s discovery of radiation from uranium salts
Marie and Pierre Curie’s discovery of polonium and radium
comment on the widespread occurrence of radioactivity

3. Learning Outcomes
distinguish between a chemical reaction and a nuclear reaction (simple equations required, confine to α and β emissions)
state three uses of radioactivity, including food irradiation and the use of 60Co for cancer treatment
explain how 14C is used for age determination (calculations not required)

4. 1.3 Radioactivity
The spontaneous breaking up of an unstable nucleus with the emission of one or more types of radiation
Discovered by Henri Becquerel

5. Radioactivity Radiation – Two Types Nonionizing
Ultraviolet, visible, infrared, microwaves, radio & TV, power transmission
Ionizing – More Dangerous
Radiation capable for producing ions [bonds broken] when interacting with matter – x-rays, alpha, beta, gamma, cosmic rays

6. Radioactivity Which Elements Are Radioactive?
Most elements have radioactive isotopes BUT any element with an atomic number greater than 83 consists entirely of radioactive isotopes
Uranium is the heaviest naturally occurring element – most elements above 92 are artificially created in nuclear research facilities

7. Radioactivity Pierre and Marie Curie Purified pitchblende
Discovered two new elements
Polonium [after Poland] and
Radium [giver of rays]

8. Alpha Particles + + Attracted to –ve charge so positive
Consists of 2 protons and 2 neutrons [Helium nucleus]
Thrown out by unstable radioactive nuclei until they become stable
Not very penetrating – Stopped by a few cm of air or a sheet of paper
Americium 241 is used in smoke alarms

9. Beta Particles Attracted to +ve plate so are negative
Simply high energy electrons
Formed when a neutron is changed to form a proton plus an electron
Electron is then ejected from the nucleus.
More penetrating – pass through paper and up to about 5mm of Aluminium
Carbon-14 emits beta particles

10. Gamma Rays High energy electromagnetic radiation - similar to X-rays
Pass straight through electric and magnetic fields so not charged.
Very penetrating – only stopped by thick layer of lead
Very dangerous carcinogenic
Can also be used to cure cancer.
Sterilising surgical instruments
Cobalt-60 is a source.

11. Widespread occurrence
Everywhere
From sun
Radon from granite
14C from bones

12. Types of Radiation

13. Types of Radiation

14. Nuclear Reactions
Radiation is emitted from the nucleus so it is called a nuclear reaction.
Totally different from chemical reaction
Chemical reactions only involve electrons
no new elements involved
atoms only rearranged
Nuclear reactions form a new element
what the alchemists tried to do.

15. Radium 226 88226 Ra emits an alpha particle
i.e. 2 P + 2 N [essentially a helium atom]
Mass number decreases by 4 to 222 because 4 nucleons lost
Atomic number decreases by 2 to 86 because 2 protons lost

16. Since atomic number determines what the element is - the element changes
When an atom loses an alpha particle it changes into the element two places before it in the Periodic Table
The Mass Number of the parent atom decreases by 4
226 Ra  Rn + 4 He
Radium  Radon-222 plus an  particle

17. Carbon-14 Loses a beta particle
A beta particle is an electron formed when a neutron becomes a proton plus an electron
Mass stays same
Atomic number goes up by one
14 C  N e-
Carbon-14  Nitrogen beta particle

18. Radioactive Equations

19. Transmutation
When an atom loses a beta particle it changes into an atom of the element one after it in the Periodic Table.
Its mass number remains the same since the neutron has become the proton
The changing of one element to another is called Transmutation.
This is very difficult to do artificially.

20. Cobalt-60
Emits gamma radiation
The loss of gamma radiation does not give rise to any new atoms
It is simply the loss of energy.

21. Radio-Isotopes
Half Life and Uses

22. Isotopes are atoms of an element which have the same atomic number [number of protons] but different mass numbers due to different numbers of neutrons
Radio-isotopes are isotopes which are unstable and give out radiation

23. Half-Life Emission purely random
To compare rates of decay we use the half-life
Half-Life is the time taken for half of the nuclei in any given sample to decay
Each radioactive isotope decays at its own rate
Some isotopes are stable while others are radioactive

24. Geiger-Muller tube measures radioactivity
Some examples of half-lives
14 C years
60Co years
234Po milliseconds

25. Uses of Radio-isotopes
1. Archaeological use
Carbon Dating
Start by finding out the half-life. [14C = 5700 years]
Measure today’s value for test material
Draw graph of radioactivity against time starting at today’s value

26. 2. Medical uses 3. Food Irradiation
Gamma rays from 60Co are used to kill tumours
Sterilise medical equipment
3. Food Irradiation
Gamma rays kill bacteria and fungi and so greatly delay decomposition of fruit etc.
This gives a far longer shelf life.
This does NOT make the food radioactive.

28. Radioactivity around us
Granite gives off Radon gas which is radioactive.
If it builds up in houses we breathe it in and it comes into contact with our sensitive membranes and can do damage.
Radioactivity is spread throughout the world because of bombs and nuclear tests and accidents.