Ionisation – occurs when an atom loses electrons.

Thermionic Emission - is the giving off of electrons from the surface of a hot metal.

Photoelectric Effect – is the emission of electrons from a metal due to light of a suitable frequency falling upon it.

Photon – is a discrete amount (packet) of electromagnetic radiation.

Electron Volt – is the energy lost or gained by an electron when it moves through a potential difference of one volt.

Atomic Number – of an atom tells us the number of protons present in the atom.

Mass Number – of an atom tells us the number of protons plus neutrons present in the atom.

Isotopes – are atoms which have the same Atomic Number but different Mass Numbers.

Radioactivity – is the disintegration of unstable nuclei with the emission of alpha, beta or gamma radiation.

Half-life – of an element is the time taken for half of the nuclei in a sample to decay.

Law of Radioactive Decay – states that the number of disintegrations per second is proportional to the number of nuclei present.

Mass Number – of any element expressed in grams contains Avogadro’s Number of atoms.

Nuclear Fission – is the breaking up of a large nucleus into two smaller nuclei with the release of energy.

Nuclear Fusion – is the joining together of two small nuclei to form one larger nucleus with the release of energy and neutrons.