Key Terms

• Activity

  The rate at which an unstable nucleus decays.
• Alpha Particle

  A positively charged particle consisting of two protons and two neutrons.
• Atomic number

  The amount of protons/electrons found in a single element. Each element has a different atomic number.
• Background Radiation

  Radiation that's found in small quantities all around us and originates from natural sources such as rocks and cosmic rays, as well as from man made sources, such as nuclear power stations or accidents (Chernobyl).
• Becquerel

  The unit of radioactive activity.
• Beta Particle


  A high speed electron that a nucleus emits when a neutron converts into a proton.
• Bohr Model

  A model that suggests that electrons orbit the nucleus at set distances.
• Chain Reaction

  The process of neutrons released by a fission reaction, being absorbed by another large, unstable nuclei and including further fission.
• Count rate

  The number of decays that a detector measures per second.
• Electrons

  A negatively charged constituent of the atom, that are found in different energy levels, around the nucleus.
• Energy levels

  The stable states which electrons are found in around the nucleus. Electrons can transition to a higher energy level through the absorption of electromagnetic Radiation and to a lower level by emitting the electromagnetic Radiation.
• Fission products

  Fission produces two smaller nuclei, two or three neutrons, and gamma rays, all released with kinetic energy.
• Gamma ray

  Electromagnetic Radiation emitted from a nucleus
• Geiger-Multer tube

  A detector that measures the count rate of a radioactive sample.
• Half-life

  The time it takes for the number of unstable nuclei of an isotope in a sample or the initial count rate of a sample of an isotope to halve.
• Ions

  Atoms with a resultant charge due to the loss of gain of electrons.
• Irradiation

  The process of an object becoming exposed to radiation. The object doesn't become radioactive.
• Isotopes

  Atoms with the same number of protons but a different number of neutrons. (Atomic number stays same, Mass number changes)
• Mass Number

  The number of protons and neutrons within an atom.
• Negative Ions

  Atoms that gained electrons so have a negative charge.
• Neutrons

  A neutrally charged constituent of the atom.
• Nuclear Explosions

  Nuclear Explosions in nuclear weapons are caused by an uncontrolled chain reaction which results in vast quantities of energy being produced in a short amount of time.
• Nuclear Fission

  The splitting of a large and unstable nucleus into two smaller and more stable nuclei to produce more energy.
• Nuclear fusion

  The joining of two small, light nuclei to form a larger, heavier one and release energy.
• Nucleus

  The positively charged centre of the atom containing protons and neutrons.
• Plum Pudding Model

  An old model of the atoms that represented the atoms as a ball of positive charge, with negative charge distributed through it.
• Positive Ions

  Atoms that have lost electrons so have an overall resultant positive charge.
• Protons

  A positively charged constituent of the atom.
• Radioactive Contamination

  The unwanted presence of radioactive atoms on other materials. It is hazardous due to the decay of the contaminating atoms.
• Radioactive Decay

  The random process involving unstable nuclei emitting radiation to become more stable.
• Sieverts

  The unit used for radiation dosage.
• Spontaneous Fission

  Fission that occurs without the absorption of a neutron. Spontaneous Fission is rare and Fission most commonly is induced with a neutron.