7.5 describe the nature of alpha and beta particles and gamma rays and recall that they may be distinguished in terms of penetrating power

NOTE: so I just wrote down about everything I could find/knew on alpha and beta particles and gamma rays, there is no need to learn all of it but I put it all down so you can choose which parts to learn, it may be an idea to learn 3-4 facts about each or at least the main distinguishing features.

Alpha particles are made up os 2 protons and 2 neutrons - this means they are 'big' and heavy, and move quite slowly too. Because of this, they don't penetrate far into materials, however, they are strongly ionising (due to there size). This means that they collide with a lot of atoms and knock off their electrons, this creates lots of ions (hence the term 'ionising'). Due to the fact they are made of 2protons and 2 neutrons, they have a positive electric charge, because of this, they are deflected by electric and magnetic fields. Because of their composition (of 2 neutrons ad 2 protons), if an atom emits an alpha particle, its atomic number will decrease by 2 (as 2 protons will have 'gone') and its mass number will decrease by 4 (as. altogether, 4 nucleons have 'gone').

Beta particles are comprised of an electron. A beta particle is just an electron which has been emitted from the nucleus of an atom when a neutron turns into a proton and an electron...bit confusing (it basically just helps to balance the charge). They are quite small and move fairly fast, therefore they penetrate materials quite far (but not super far) and are quite ionising too (but not as much as alpha particles). When a nucleus emits an electron the number of protons in the nucleus will increase by 1, meaning the atomic number increases by 1 but the mass number stays the same (i don't really understand this it... help). Because beta particles are negatively charged (as they are comprised on one electron), they are deflected by electric and magnetic fields (like alpha particles).

Gamma rays have no mass, they are just made of energy and therefore can penetrate far into materials without colliding into anything - this means they very weakly ionise, as they often pass through instead of hit atoms (although they eventually hit one, therefore they are not not-ionising). Since they have no mass, they have no charge, therefore they are not deflected by electric or magnetic fields. the emission of gamma rays has no effect on the proton or mass number of an isotope, as it has no mass. If a nucleus has too much energy, this is when a gamma ray is emitted (as it is just made up of energy, so emitting it will 'get rid' of all the excess energy).

NOTE: Gamma rays are only emitted after either alpha or beta particles (or maybe both), they are never emitted by themselves.

Since each type of radiation penetrates a material to different extents, it is easy to identify what it is by its penetrating power.
- If it is stopped by thin materials, such as paper or skin, it is alpha.
- If it is stopped by mediumish thickness materials, such as a sheet of aluminium, but can pass through paper, it is beta
- If it can pass through paper and aluminium but not thick lead, it is gamma.

Here is a diagram that may help for understanding purposes...


image source: gtcceis.gov