fission and fusion two types of nuclear reactions so we're gonna start with fission fission is um basically when a neutron hits the nucleus of an atom so here's where you see the uranium it happening with uranium so if we use that as an example a neutron it hits uranium makes it unstable so a previously like stable um nuclei and then adding a neutron to it increases the mass which can therefore make it unstable and once you do that an atom will split so what happens is when it splits it splits in two or three different atoms that are smaller that sort of all make up the same mass as that original one but they split and make smaller atoms so that's kind of what you can see here i know it's hard to see in the picture the examples will be a little bigger but here you can see the uranium which got hit by a neutron the uranium split into xenon and does that say rubidium i can't i can't see um anyway um so that's what fission is it's taking a large nuclei and making smaller nuclei um the critical mass is the point at which the reaction can be sustained so we do call this a chain reaction because when the atom is splitting that's what these other little arrows are they're neutrons that are coming off so as it splits it releases a few more neutrons those neutrons hit other atoms and so forth um if i didn't have those neutrons coming off like if i didn't have two or three however many if i just had one and it just hit one other atom and then that atom released one um eventually that could sort of fizzle out right if that one neutron missed the next atom so there is such thing as critical mass which means we need a minimum amount of material to just to sustain this chain reaction to keep it going we can control it that's how we do nuclear power is we control one of these vision reactions um we do that with um uranium-238 you can also use it in a bomb format actually like um nuclear bombs usually use a combination of fission and fusion um let's see when you break up the uranium into two or three smaller particles if you were to go backwards and sort of add those smaller particles together to get the mass of the large one you might find a little bit of mass missing we call that the mass defect and we can calculate how much energy that little bit of mass is going to give us based on the equals mc square k equation where c is the speed of light m is the mass defect so that little bit of mass that went missing and then e is the energy so that little bit of mass can give us a lot of energy based on this equation fusion does the same thing where again we get a little bit of mass and it gives us a lot of energy we actually get a lot more energy from fusion than we do from fission um and it happens at like uh at a like instant so when we use a nuclear bomb we're usually using a fission reaction to start a fusion one so in fusion it's kind of exactly what it says like fission you kind of think of fizzling out like getting smaller fusion is taking those smaller ones and putting together and making a larger atom um nuclear fusion is how we make atoms in real life like there's man-made elements on the periodic table we've done that through like fusion type reactions they always form a heavier nuclei they release again a lot more time a lot of times more energy than fission this is the process occurring in the sun again we can also make um a bomb the hydrogen bomb is started by having a fission reaction that starts the like fusion explosion and we all hear about like cold fusion so fusion typically has to happen at really really high temperatures hence it happens in the sun it also creates a lot of energy um so the idea of cold fusion violates that law of thermodynamics and laws we know are proven and can't be changed so there are four main types of radioactive particles there are actually quite a few more but these are the four that we're going to focus on so beta emission this is where a nuclei becomes unstable and what happens is one of the neutrons a neutron it has a neutral charge and in beta emission that neutron splits so when that happens this neutron right here this like blue dot is going to split into a positive and a negative well we know in the nucleus of an atom we can only have positive we can't have negative so that neutron then turns into a proton so it turns into something that's positive and it kicks out that negative that negative that it kicks out is what we call a beta particle so that's beta decay alpha decay is the basically the nucleus of a helium atom so if i had a nucleus and it lost two protons and two neutrons that would be an alpha particle this is the symbol for an alpha particle uh gamma is just energy so it's not a particle at all and then neutron is again when it releases a neutron so it just releases mass you can see here i have beryllium 13 and i went down to beryllium-12 because i lost a neutron uh we'll see you'll see some more or you'll see how to use that in sort of an equation format in the um in the uh in the uh examples and then finally we talked a lot about like once a particle becomes unstable this is when it's going to emit a neutron or when the neutron is going to split or where we're gonna have like a fission reaction um so how do we know how do we know if like an atom has enough neutrons that it's become unstable or has too few neutrons so it's unstable there's like this this very specific amount where uh it can be stable that's what you see here in this picture you see like this what we call like a band of stability where if you're in between this number of neutrons and this number of protons like you're in this like green light area where you have stability great but if you have too few protons or too few neutrons or too many or two less or whatever if it's not like a a balanced amount then we're outside of that band of stability and all of those things can go through different types of decay so neutron beta decay alpha decay and i know this says positron emission and electron capture those are remember on this slide i said we had four we were going to focus on those are other things that can happen as well um this is how we calculate if something is stable so we're going to take the number of protons and then we're going to multiply that by 1.5 and if our number of neutrons fall within that range then it's stable if they're not within that range then it's unstable so i'm going to do an example carbon-14 so based on the periodic table right here i can see that carbon has six protons and in hyphen notation that 14 is the mass number so we know protons and neutrons equals mass so if carbon has six protons then neutrons equals the mass number minus the protons right mass equals neutron trons plus protons so if i just arrange that equation appropriately my neutrons is the mass number so 14 minus the number of protons which is six which means i get eight so here i just went ahead and put a six for protons i multiplied six by one point five and got nine and then i did my formula to find the number of neutrons and i got eight this statement is true therefore it's stable if i did this and i got 10 here then that would be unstable if i did it and i got like five here it would be unstable so if this statement is not true it's unstable if it is true it's stable so that's how you can calculate if something's going to be stable or unstable based on the mass number and that's it so head on over to your digital notebook and there'll be a few examples on there you can check out but that's about it thanks