 Okay, so let's do a couple of these other types of problems Less involved this one says the subscript giving the atomic number of an atom is often left off when writing an isotope symbol for example Carbon 13 is Carbon 13 written like this is often written just like This that's carbon 13. Why is this allowed? Okay, so Since since it's carbon right it has to have six protons is what it's saying You know so any isotope of carbon is going to have six protons. It's just the number of neutron that's changed Okay, so in fact what they're really saying is this see and this six are redundant information Does that make sense? So every time you have a see here. It has to have six protons for example if I have How many protons does this molecule have or this atom have sorry? Six right and this one here Six but how many neutrons does this one? six So that's the mass number on top. Okay, the mass number so how many neutrons does this one? Seven right okay because so let's just do it one more time right so protons, right? How many does this one have? Protons six How many does this one? And how do you know that? Because it's carbon, right? It's carbon, right? So the number of neutrons. How many does this one have? Seven right and this one Six and why is that because these two numbers have to equal the mass number. Any questions on that? questions you sure No, yeah, like I was saying if you think electrons are like 10,000 times as small as the proton or Weight wise, you know, so like it's like you getting on the the balance at the gym You know or the scale of the gym looking at your weight and saying, okay, I weigh 190 pounds, you know or something like that and then Fly lands on you know, does that change your weight any significant? Probably not, you know Everybody okay with that so electrons? No no way