Types of Radioactive Decay (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)): Revision Note

Types of radioactive decay

• Radioactive decay is a change in an unstable nucleus that can result in the emission of one of the following types of radiation:

  • Alpha (α) particles

  • Beta (β^-) particles

  • Gamma (γ) radiation

• Remember that these changes are spontaneous and random

Alpha particles

• The radiation symbol for alpha is α

• An alpha particle is the same as a helium nucleus

  • This is because they consist of two neutrons and two protons

• Alpha particles have a charge of +2

  • This means they can be affected by an electric field

Beta particles

• The radiation symbol for beta is β^-

• Beta particles are fast-moving electrons

• They are produced in nuclei when a neutron changes into a proton and an electron

• Beta particles have a charge of -1

  • This means they can be affected by an electric field

Gamma rays

• The radiation symbol for gamma is γ

• Gamma rays are electromagnetic waves

• They have the highest energy of the different types of electromagnetic waves

• Gamma rays have no charge

Types of radioactive decay

Alpha particles, beta particles and gamma waves can be emitted from unstable nuclei

Alpha, beta & gamma emission

• α, β and γ radiation can be identified by the emission from a nucleus by recalling their:

  • Nature (what type of particle or radiation they are)

  • Their relative ionising effects (how easily they ionise other atoms)

  • Their relative penetrating abilities (how far can they travel before they are stopped completely)

• The properties of alpha, beta and gamma are given in the table which shows the trend down the table as:

  • The range increases

  • Penetrating power increases

  • Ionisation decreases

Summary of the properties of nuclear radiation

Penetrating power

• Alpha, beta and gamma radiation have different properties

• So they penetrate materials in different ways

  • This means they are each stopped by different materials

Penetrating power of alpha, beta and gamma radiation

Alpha, beta and gamma are different in how they penetrate materials. Alpha is the least penetrating, and gamma is the most penetrating

• Alpha is stopped by paper, whereas beta and gamma pass through it

• Beta is stopped by a few millimetres of aluminium

  • Gamma can pass through aluminium

• Gamma rays are only partially stopped by thick lead