Radioactivity is caused by unstable atomic nuclei that emit radiation to achieve stability. There are three main types of radiation emitted - alpha particles, beta particles, and gamma rays. Alpha particles have a strong ionizing power but can only travel a short distance, while gamma rays have a very weak ionizing power but can travel farther. The half-life of a radioactive isotope is the time it takes for half the nuclei in a sample to decay.

1. Radioactivity

2. Key terms
• Atom
• Nucleus
• Protons
• Neutrons
• Ions
• Atomic number
• Mass number
• Radioactive
• Radiation
• Alpha particle
• Beta particle
• Gamma particle
• Ionising power
• Isotope
• Half-life
• Penetration
• Deflection/ deflected

6. Radioactivity: industrial applications
What is radiation?
The nuclei of some atoms are unstable. In order to achieve stability
they emit radiation.
These materials are called radionuclides.
They are radioactive.
Radioactivity is a nuclear process – it is not a chemical process. It is
not possible to control the rate of radioactive breakdown of a
nuclei, it is a random process

7. Background radiation

8. Atomic structure
Atoms consist of a nucleus and electrons
The nucleus is made up of protons and neutrons
Blockbusters game

9. Characteristics of alpha, beta and gamma radiations
There are three types of radiation that can be emitted from a nucleus
of an unstable atom.
Alpha (α)and beta (β) are particles of matter
Gamma (γ) rays are photon of electromagnetic radiation, with a
higher frequency than an x-ray.

10. Characteristics of alpha, beta (β+ and β–) and gamma
radiations
Particle Constituent Charge Mass
Alpha (α) Helium nucleus
2 protons and 2
neutrons
+2 4
Beta- minus (β-) Electron -1 Negligible
Gamma (γ) Short-wave, high
frequency em wave
0 0

11. Particle Ionising Range Speed Affected by
magnetic field?
Alpha (α) Strong –easily pull
electrons off atoms
(10 000 ionisations
per particle)
Slow Yes
Beta- minus (β-) Weakly (100 atoms
per particle)
Fast Yes
Gamma (γ) Very weakly Speed of light No
Gamma radiation spreads out very quickly. Its intensity decreases by the inverse square law.

12. Characteristics of alpha, beta (β+ and β–) and gamma
radiations

13. • The half-life of a radioactive isotope is defined as the
time it takes for the number of nuclei of the isotope in a
sample to halve or the time it takes for the count rate
from a sample containing the isotope to fall to half its
initial level.

14. Half-life