Electron capture is a type of decay in which the nucleus of an atom draws in an inner shell electron. Electron capture occurs when neutrons and protons are below the band of stability, but there is not enough energy to emit a positron.
Alright, so one of the nuclear reactions that you might come across in class is going to be electron capture as known as k capture and that's when the nucleus of an atom draws in an inner shell electron hence the name electron capture. So when does this happen? This happens when the neutron and proton ratio is too low or below the band of stability so if we go over and look at the band of stability, here is the [IB] the ratio is 1 to 1 is lower red line, here's when the ratio is 1.5 to 1 so at low atomic numbers they're going to be 1 to 1 high atomic numbers are going to be 1.5 and this great area is where things are stable okay so this is when it's below and it's low down here it's going to get through electron capture, so that means we have too many protons, we have to get rid of some protons somehow, so what do we do?
Well what's going to happen is a proton is going pull in and suck in the nucleus so suck in an inner shell electron and it will react with the proton within the nucleus and it's going to turn that turn this these two things into a neutron so that's going to add a neutron to this. It will release some energy some x, x-rays and some gamma rays out in the atmosphere when it does this okay?
So let's look at this, we have rubidium has a mass number of 81 and an atomic number of 37 and if we look at the neutron to proton ratio, it's 44 and 37 which is about 1.19. Now this is kind of tricky I had to actually look at the graph to see specifically what it should be. But approximately it should actually about 1.25 this is a little bit too low so what we're going to do is we're going to suck in an inner shell electron and we're going to change this we're going to mutate this rubidium and we're going to change it to krypton and so we're going be the atomic number is going to lower 1 and the mass number will be the same and since the krypton with the atomic number with the mass number of 81. Let's check out the neutron to proton ratio for that one so 1.25 which is about which is right above the where it should be and it will emit some x-rays and some gamma rays off them. So this is a good example of electron capture and notice that the atomic numbers sorry the atomic numbers will equal up and the mass numbers will equal up if we make sure that are where the arrow sign is an equals number.
So this is one of the things you'll come across when dealing with nuclear reaction.