So how many grams do 20 calcium atoms? So 20 calcium. How many grams do they do? So let's write down what the problem says. So we've got calcium. And we've got 20 atoms. So what do we know about one atom of calcium and how much it weighs? So we've looked at the periodic table and we've got it converged right one atom of calcium equals 40.0A. We'll say AMU. And we already know this other converged detector that was given to us 1A and mu to grams. So we should be able to put these 2 in a row to get this mass. Is everybody okay with that? So it gave us the problem, gave us the number of calcium atoms. So we'll say 20 calcium atoms. So again it's good for you to, you know, if you're having trouble with what units go on the bottom, go on the top, write the whole thing out. So the problem, sorry, the problem, give us. When it's 20 like this, right I should have said something. That's an infinite number of significant figures. It's just like counting how many students do have in this room. 1, 2, 3, 4, 5, 6, 7, 8, not 8.3 something. So that's an infinite number of significant. So in actuality, this problem, you could give it to us. Many significant figures as you want. Finally, if that's okay. It's common to go to like three or four. So anyways, so do we have a conversion that goes from atoms to amu? Yes. So one atom of calcium is 40.08 amu or one calcium atom. And then of course we do the conversion factor that we used in the problem previous. And say, 1 atom, you with the bottom, 126, 6, 1, 10 to the negative 24 grams on the top. So will we expect this to be a lot of grams or a tiny amount of grams? Small amount. Because four calcium atoms, very tiny, very tiny. Or 20 calcium atoms, very tiny. 4 is also very tiny. So let's just plug in. So 20 times 40.08. So this one you would expect to get a negative x one. So again, I'm going to take this to four six things just because of 1.331 times 10 to the negative 20 grams. Okay, so that's how many grams, 20 calcium atoms was. Hopefully it makes sense. Right? So it's very much smaller than 1.