 Okay, so let's go ahead and try this one number, the third one on the quiz. It says a helium nucleus has two protons and two neutrons. How many electrons would it take to equal the mass of a helium nucleus? And it gives you the mass of a proton, a neutron, and an electron. So some of us did this some weird way, trying to go periodic table, looking at the mass of helium and all that. That's not one of the way to, and then converting grams to AMU, and don't do it that way, okay? They give you this information and they tell you the helium nucleus has two neutrons and two protons, okay? So how do I do that? Well, the mass of the helium nucleus is going to be two times this number, because that's one proton. So 1.67262 times 10 to the negative 27 kilograms. And then add that to two times the mass of a neutron, right? And you have two protons and two neutrons. So 1.67493 times 10 to the negative 27 kilograms. And the first thing we want to do is figure out the mass of that nucleus, okay? And so let's do that together. Plug in your calculator. And I get a number, 3, 4, 5, 6. Everybody okay with what I've done? Times 10 to the negative 27 kilograms. Okay, so that's the mass of a helium nucleus. Okay, with what I've just done? Okay, cool. So a lot of people got to that part, but it's this next step that was a part, okay? Because it's asking us how many electrons equals that mass. Well, we have a conversion factor. We got to always remember when something equals something else, that's a conversion factor. Okay, so what are we really trying to do now? We're trying to find the number of electrons in this mass, okay? So what we're just going to want to do is write down that number again. 6.69510 times 10 to the negative 27 kilograms. And then we know one electron equals that many kilograms. So we just take that. But kilograms at the bottom, 0.0091 times 10 to the negative 27 kilograms. And the number of electrons that that mass equals is how many? One electron, right? Is everybody with me? Ain't nobody going to say anything. Just going to chuck. Okay, so when we see that, we can now cancel out our kilograms. Is everybody okay with that? So now, Harlan, remember, I talked to you about this the other day. When we're counting things, if I'm counting the number of students in my classroom, right? And I say, well, I have 15.67 students. Does that make any sense? What about 15.53 or 12.41, okay? Electrons are little discrete entities, okay? So when you count the number, it's got to be a whole number, okay? So yes, I agree that we're going to get some number with some decimal points. We've got to round that to the whole number, okay? So we take that, divide this, this number that we got by this number, 0, 0, 0, 9, 1, negative 27. And what do I get? Hopefully the same thing as you. What did we get, guys? 7,500. Yep, 7,357 point whatever, right? In my case, 25. Okay, there's no such thing as a quarter of an electron. But we also want to remember our units, so electrons, okay? Or if you want to put... So again, I think when we start off the class, we're learning conversion factors, you know? So this problem is helping us to identify that anything that we see that's an equivalency can be used as conversion factors, okay? So just take that to heart when you're doing this, because I know oftentimes when there's all these weird numbers to the negative 27, 0, 0, and all that craziness, it kind of throws you off from the main point of the problem which is just using your conversion factor, okay? Any questions on this one? Wonderful.