Across
- 1. Atoms that gained electrons and so have a resultant negative charge.
- 3. A material that reacts to ionising radiation, allowing an image to be formed.
- 7. A barrier used to prevent radioactive daughter products leaving a nuclear reactor.
- 9. The process of neutrons released by a fission reaction, being absorbed by another unstable, large nuclei, and inducing further fission.
- 10. Atoms that have lost electrons and so have a resultant positive charge.
- 16. A positively charged particle consisting of two protons and two neutrons. They are highly ionising, but can be stopped by a few centimetres of air.
- 17. A negatively charged constituent of the atom, that are found in different energy levels, around the nucleus.
- 21. A high speed electron that a nucleus emits when a neutron converts into a proton. They are ionising but can be stopped by a thin sheet of aluminium.
- 22. The radioactive isotope used in nuclear reactors. It is often referred to as U-235.
- 23. Atoms with the same number of protons but different numbers of neutrons. The atomic number is the same, but the mass number is different.
- 26. Radiation that can cause cell mutations, damage cells and tissues, and lead to cancers.
- 28. The random process involving unstable nuclei emitting radiation to become more stable.
- 29. The number of protons found in an atom of a specific element. Each element has a different atomic number.
Down
- 2. The process of an object being exposed to nuclear radiation. The object doesn’t become radioactive.
- 4. Atoms with a resultant charge due to the loss or gain of electrons.
- 5. All matter has an associated energy. This means that mass can be converted into energy in the form of radiation.
- 6. The unwanted presence of radioactive atoms on other materials. It is hazardous due to the decay of the contaminating atoms.
- 8. The rate at which an unstable nucleus decays.
- 11. A medical imaging device that uses radioactive tracers and detectors to form internal body images.
- 12. The stable states in which electrons are found in around a nucleus. Electrons can transition to a higher energy level through the absorption of electromagnetic radiation and can transition to a lower energy level through the emission of electromagnetic radiation.
- 13. The time it takes for the number of unstable nuclei of an isotope in a sample to halve, or the time it takes for the initial count rate of a sample of the isotope to halve. It is different for different isotopes.
- 14. The joining of two small, light nuclei to form a larger, heavier one and release energy. It cannot happen at low pressures and temperatures since in these conditions the electrostatic repulsion of protons in the nucleus cannot be overcome.
- 15. The number of protons and neutrons in an atom.
- 18. A neutrally charged constituent of the nucleus.
- 19. Electromagnetic radiation emitted from a nucleus. They have a very high penetrating power and require several centimetre of lead to absorb them.
- 20. Products: Fission produces two smaller nuclei, two or three neutrons and gamma rays. These products are released with kinetic energy.
- 24. A positively charged constituent of the nucleus.
- 25. Radiation that is 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 weapons testing and accidents.
- 27. The splitting of a large and unstable nucleus into two smaller and more stable nuclei to produce energy. This is the method currently used in nuclear power stations.