Atoms and Radiation
- A concept of I/GCSE physics, Isotopes are atoms with the same number of protons but a different number of neutrons. A good example of an isotope is carbon 12, carbon 13 and carbon 14. As you can see from the diagram below, the proton number NEVER changes. This is because the proton number determines what element the atom is, so if you were to change the proton number of carbon, it would no longer be a carbon atom. However, the diagrams show the neutron number changing for different isotopes of carbon.
- Most elements have different isotopes, but there are only a few stable ones. The rest are usually radioactive meaning they decay into other elements whilst giving out radiation.
- Radioactive substances give out radiation from the nuclei of their atoms.You’ve got to remember that radioactive decay is a completely random process. It happens whenever. There are no special circumstances where we can make it speed up or slow down. When a substance is giving out radiation, it either gives out alpha particles, beta particles or gamma rays.
- This happens all the time around us which is known as background radiation.Sometimes there are naturally occurring unstable isotopes around us found in the air, in food, in rocks, etc. Radioactivity also comes from the space in this way, mostly from the sun, which is more commonly known as cosmic rays. There is a lot of background radiation from man-made sources for example, nuclear accidents, or from nuclear weapons. The most important thing to remember is that radioactive decay is always happening around us.
- For the course, you have to know the properties of each of the three types of radiation, so a quick way to remember them is using the table below. It covers all the properties you need to know.
The table explained in words:
- Alpha particles are big, heavy and move slowly;therefore they can’t penetrate very far into materials. This also means they are stopped quickly when moving through air. They are strongly ionising due to their size. They can easily hit other atoms and knock electrons off of the other atoms before they slow down. This causes the atoms they hit to become ions –because they lose electrons causing them to become charged.
- Beta particles move quite fast and are quite small. They can penetrate moderately into materials before colliding, have a long range inair and are moderately ionising too.When a beta particle is emitted from the nucleus of an isotope, a neutron turns into a proton, causing the element to change to a different element.
- Gamma rays can penetrate far into materials without being stopped and they can pass easily through air. They are very weak at ionising because they pass through substances rather than collide with atoms. However, if they do manage to hit something, they do cause damage.
And we're all done for today!
Drafted by Kin (Physics)