Now before we talk about alpha decay and nuclear fission, it's important to understand that isotopes that lie outside the band or valley of stability are considered unstable radioactive isotope. And we're going to say these isotopes will alter their number of neutrons and or protons to move closer to the band or valley of stability.
Now we know they do this predominantly based on our header that they do it through alpha decay and nuclear fission, but they can also do it through beta decay. They can do it through electron capture or even positron emission. So these are just the different avenues that our particular isotope can take in order to get closer and fall within the band of stability and reach a greater level of nuclear stability.
So keep this in mind when looking at any isotope and comparing it onto the neutron to proton plot.