1. Radioactive materials

2. The nucleus is positively charged
electron -
An atom
proton +
neutron 0
nucleus
orbit / shell
energy level
Animation completed
The nucleus is positively charged
so it attracts the negative electron

3. Alpha particles (positive charge)
How do scientists know about the structure of atoms?
The Rutherford Scattering Experiment
Alpha particles (positive charge)
Thin gold foil
Some particles passed through, some were deflected backwards
Particles passing through the foil indicated atoms have large amounts of space.
The particles that were deflected back indicated the alpha particles had passed
close to something positively charged within the atom (the nucleus)

4. Radioactive isotopes release radiation and the nucleus changes
When an unstable nucleus changes, what can happen ?
alpha radiation
nucleus
beta radiation
gamma radiation
Radioactive isotopes release radiation and the nucleus changes
The behaviour of radioactive materials (radioactive decay) cannot be changed by chemical or physical processes

5. Isotopes An isotope is an atom with a different number of neutrons:
A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating.
Radioactive changes – some nuclei that are unstable
can become stable by emitting an alpha or beta particle
1) Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom)
2) Beta () – an atom decays into a new atom by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.
3) Gamma – after  or  decay surplus energy is sometimes emitted. This is called gamma radiation and has a very high frequency with short wavelength. The atom is not changed.

6. Alpha decay
Example
Radium-226 undergoing alpha decay forms Radon-222, an alpha particle and releases energy.
Beta decay
Example
Polonium-218 undergoing beta decay forms Astatine-218, an electron and releases energy.

7. Radioactivity
If a substance is capable of ALWAYS emitting radiation under any conditions we say it is radioactive. There are three types of radiation: ALPHA, BETA and GAMMA.   
Sheet of paper
Few mm of aluminium
Few cm of lead

8. Sources of background radiation
Radiation dose measures the possible harm the radiation could do to the body. It is measures in millisieverts (mSv).
The potential harm done depends on
the amount of radiation
the type of radiation

9. Exposure to a radiation source outside your body is called irradiation
If a radiation source enters your body, or gets on skin
or clothes, it is called contamination
Alpha particles are the most ionising so they are the
most dangerous inside your body
Employers must ensure that radiation workers receive a
Radiation dose “as low as reasonably achievable”.
Precautions taken are
use protective clothing and screens
.wear gloves and aprons
wear special devices to monitor their dose

10. treating cancer Uses of gamma radiation sterilising equipment
sterilising food
it can kill cancer cells
it can kill microbes without harming the food
it can penetrate the outer casing and kill microbes

11. Radon gas is harmful because it is radioactive. It
produces ionising radiation that can damage cells.
Medical imaging and treatment
Radioactive materials cane be used to diagnose and
cure many health problems.
Radiotherapy is used to kill cancer cells

12. Half life
The HALF-LIFE of an atom is the time taken for HALF of the radioisotopes in a sample to decay…
= radioisotope
= new atom formed
After 2 half lives another half have decayed (12 altogether)
After 3 half lives another 2 have decayed (14 altogether)
After 1 half life half have decayed (that’s 8)
At start there are 16 radioisotopes

13. A radioactive decay graph
Count
Time
1 half life
A substance is considered safe once its activity drops to the
same level as background radiation.

14. Nuclear fission neutron The energy released can be
calculated from Einstein’s
equation : E = mc²
ENERGY
neutron
U-235
nucleus
neutrons
The fission of one atom can
set off several more causing
a chain reaction
Smaller nucleus

15. High level waste – this is “spent” fuel rods
Nuclear reactor
Nuclear waste
High level waste – this is “spent” fuel rods
Intermediate level waste – HLW decays to become ILW
Low level waste – protective clothing and medical equipment

16. Nuclear fusion – the nuclei of two hydrogen atoms join
together and energy is released.
Protons and neutrons in a nucleus are held together by a
strong nuclear force, which acts against the electrical
repulsive force between protons