Types of Radiation (Edexcel GCSE Physics)

• 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

ANSWER:   C

• • Answer A is true. The number of neutrons in a nucleus determines the stability
  • Answer B is true. This is a suitable description of radioactive decay
  • Answer D is true. Radiation is about emissions. It is different to radioactive particles
  • Answer C is not true
  • Radioactive decay is a random process
  • It is not possible to predict precisely when a particular nucleus will decay

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

• 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