Radiation (SQA National 5 Chemistry): Revision Note

Radioactive decay

• Some atoms have an unstable nucleus

  • These unstable atoms are called radioisotopes.

• To become more stable, the nucleus of a radioisotope gives out radiation

  • This process is called radioactive decay

  • It involves changes only in the nucleus of the atom

• Three different types of radiation that can be emitted are:

  1. Alpha (α)

  2. Beta (β)

  3. Gamma (γ)

What are alpha, beta, and gamma radiation?

Alpha radiation

• The symbol for alpha is α

• Alpha radiation is a "particle"

• An alpha particle is the same as a helium nucleus

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

Beta radiation

• The symbol for beta is β

• Beta radiation is also a "particle"

• Beta particles are fast-moving electrons

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

Gamma radiation

• The symbol for gamma is γ

• Gamma radiation is not a "particle", it is a ray

  • Gamma rays are high-energy electromagnetic waves

Penetrating power

• Penetrating power is the ability of radiation to pass through different materials

• Each type of radiation has a different penetrating power

Alpha radiation

• Alpha radiation has low penetrating power

• It is stopped by a single sheet of paper

Beta radiation

• Beta radiation has medium penetrating power

• It can pass through paper

• But, it is stopped by a thin sheet of aluminium

Gamma radiation

• Gamma radiation has high penetrating power

• It can pass through paper and aluminium

• It is only stopped by thick barriers of lead or concrete

The three types of radiation have different abilities to pass through materials.

Effect of an electric field

• The three types of radiation have different charges

  • This means that they behave differently in an electric field

Alpha radiation

• Alpha radiation has a charge of +2

• This positive charge means that it is attracted to the negative plate in an electric field

Beta radiation

• Beta radiation has a charge of -1

• This negative charge means that it is attracted to the positive plate in an electric field

Gamma radiation

• Gamma radiation has a charge of 0

• This lack of charge means that it is not deflected and passes straight through

Summary of radiation properties