91�ȱ�

The idea of the atom as the building block of matter has developed over time. What was thought of as a single particle about 1 × 10‾¹⁰ m across is now known to be a collection of smaller particles.

Atoms are made up of protons, neutrons and electrons. Change the number of neutrons in an atom and it becomes an isotope, change the number of electrons, it becomes an ion.

With the wrong number of neutrons, nuclei can fall apart. A nucleus will regain stability by emitting alpha or beta particles and then ‘cool down’ by emitting gamma radiation.

People are exposed to sources of radiation in all aspects of everyday life. Radioactive sources can be very useful but need handling carefully to ensure safety.

The nuclei of atoms contain a large amount of energy. Releasing this energy would free the world from having to use fossil fuels. There are two methods of doing this: fission and fusion.

Understanding how to approach exam questions helps to boost exam performance. Questions will include multiple choice, descriptions and explanations, using mathematical skills, and extended writing.