So now that we've introduced isotopes in our previous lesson videos, in this video we're going to introduce radioactive isotopes. Radioactive isotopes are essentially isotopes that are very unstable and will eventually break down and emit energy in the form of rays or particles. If we take a look at our image on the left-hand side, you'll notice we're showing the radioactivity of a carbon-14 isotope. This represents the nucleus of the carbon-14 atom, and what you'll notice is that it has 6 protons, shown here in red, and 8 neutrons. We discussed the Carbon-14 isotope in some of our previous lesson videos, so that should be a bit familiar. This gives the Carbon-14 isotope a mass number of 14, which is why it's called Carbon-14. Once again, Carbon-14 is a radioactive isotope, so it is unstable and will break down, emitting energy in the form of rays or particles. This arrow here represents released energy, and this other arrow represents released subatomic particles. This process will break down and decay over time.

The rate at which radioactive atoms decay over time is quite consistent, and from this consistency, scientists can determine what's known as a half-life. The half-life is the exact amount of time it takes for half of all the radioactive atoms in a sample to break down and decay. From this half-life, scientists can use it for meaningful purposes, such as in medicine and for radiometric dating of fossils. You'll notice here in our image on the right-hand side, we're showing a person getting an MRI, which uses radioactive isotopes, and some fossils; the radiometric dating of these fossils relies on isotopes.

This concludes our brief introduction to radioactive isotopes, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you in our next video.