Here we're going to say that alpha decay happens for isotopes. In the top right corner of the neutron deproton plot, we are going to say these isotopes have an excess of neutrons and protons. If we take a look here, we have platinum 213. Here it lives within our red region, which means it wants to do alpha decay in this case.
Here we have alpha decay of platinum 213. It would emit an alpha particle as a product and as a result it will create Bidsmith 209. By doing this, we're going to say, what does it do? Well, if we look at our plot, we know that on our Y axis we have our number of neutrons. On our X axis we have our number of protons. Here it's decreasing its number of neutrons, decreasing its number of protons so that we can fall within the band or valley of stability and create a more stable isotope.
This in this case would be bismuth 209. It's giving us this green dot right here. Now this happens with isotopes with atomic masses of that are equal to or greater than 210 AMU. We're going to say this whole process is just helping to decrease the total number of nucleons, your total number of protons and neutrons, because there's an excess of both of them. OK, so in this case again removing from the top right section this red area into the more stable green area which represents our band or valley of stability.