 Okay, so for the last problem today, we'll do this. Calculate the number of mercury atoms you have if you've got 12.3 grams of mercury. So we know that mercury, the chemical symbol is Hg, and of course the atomic weight of mercury is 200.6. We'll just approximate 200.6 AMU. So we can approximate the molar mass of mercury to be 200.6 grams per mole. So if I'm looking for the number of atoms at 12.3 grams, and I know this number here, I can multiply that by the inverse of that number, which would be 200.6 grams, one mole, grams cancel, and I'm going to multiply that by the conversion factor that you know, we've got to draw this number. One mole equals 6.022 times 10 to the 23rd atoms, or anything else for that matter. Okay, so one mole 6.022 times 10 to the 23rd atoms, moles cancel, and what do I get? X, right? So is that the number of atoms? That's what we want, right? So it's atoms to atoms, yes, and it's awesome. Okay, so we go 12.3 divided by 200.6 times 6.022 times 10 to the 23rd, and we get, because we've got three sig figs, we get 3.69 times 10 to the 22nd atoms, and we should have expected it to be a very large number, okay? But not 6.022 times 10 to the 23rd, because we would need 206 grams to get that number, okay? So we should expect it to be less than that number, and it is, okay? So good job guys, kind of gets spring break, and that's that.