Types of Radiation (Edexcel GCSE Physics)

Types of Radiation

• Some atomic nuclei are unstable

• This is because of an imbalance in the forces within the nucleus

  • Forces exist between the particles in the nucleus

• Carbon-14 is an isotope of carbon which is unstable

  • It has two extra neutrons compared to stable carbon-12

• When an unstable nucleus decays it emits radiation, called nuclear radiation

Carbon-12 is stable, whereas carbon-14 is unstable. This is because carbon-14 has two extra neutrons

• Some isotopes are unstable because of their large size or because they have too many or too few neutrons

• Unstable nuclei can emit radiation to become more stable

• Radiation can be in the form of a high energy particle or wave

Unstable nuclei decay by emitting high energy particles or waves

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

  • Alpha (α)

  • Beta-minus (β^-)

  • Beta-plus (β⁺)

  • Gamma (γ)

  • Neutrons

• As the radiation moves away from the nucleus, it transfers energy away from the system

  • This reduces the overall energy of the nucleus

  • This makes the nucleus more stable

• The process of emitting radiation is called radioactive decay

• Radioactive decay is a random process

  • This means it is not possible to know exactly when a particular nucleus will decay

The Nature of Radiation

Alpha Particles

• The 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 symbol for beta is β

• Beta particles are fast-moving electrons emitted from the nucleus

• Beta-plus particles are fast-moving positrons (positive version of electrons)

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

• Beta-minus particles have a charge of -1

• Beta-plus particles have a charge of +1

  • This means they can be affected by an electric field

Gamma Rays

• The 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

Neutrons

• The symbol for a neutron is n

• Neutrons are one of the two particles found in the nucleus of atoms

• Neutrons are neutral, they have no charge

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

Ionising Radiation

• Ionisation is the process by which an atom loses an electron due to radiation

• All nuclear radiation is capable of ionising atoms that it hits

• When an atom is ionised, the number of electrons it has changes

  • This gives it a non-zero charge (the atom is left with a net positive charge)

When radiation passes close to atoms it can knock out electrons, ionising the atom

• Alpha radiation is the most ionising form of nuclear radiation

  • This is because alpha particles have a charge of +2 and is the heaviest

• Gamma radiation is the least ionising form of nuclear radiation