 Okay, so let's try to determine how many hydrogen atoms are on each one of these other atoms, and why are these particular atoms pictured, okay? So this is the bond line structure of serotonin. So if I point to an atom, I want you to tell me what it is, okay? So this one here, carbon, how many hydrogens are attached to that carbon? Two. Two. How do you know that? It's got one carbon bonded to it and one nitrogen bonded to it, okay? So watch out, so you don't think that that in between there is a carbon, that's a common problem for introductory students, okay? So why am I showing this atom if I'm not showing the carbon atom? Because I have to because it's a heteroatom, right, and heteroatoms have to be pictured, okay? Why am I showing hydrogen here but not here? Because when it's bonded to a heteroatom, it's not implied, okay? It's only implied when it's bonded to a carbon, okay? So let's go over these carbons. Tell me when I point to it how many hydrogens it's got, okay? So, okay. One, right? How many bonds does it have already? Three. One, two, three, right? So one hydrogen. Everybody cool with that? Mm-hmm. Why am I showing this hydrogen if I'm not showing this one? Because it's bonded to a heteroatom, okay? How many hydrogens are here? One. One, okay? This is a common structure, it's called a benzene ring, okay? So, have you ever heard of that structure or that molecule benzene? That's what benzene looks like. How many hydrogens are on each of those carbons in benzene? One, right? What's the molecular formula for benzene? Yeah, very good. C6H6, like that. That makes sense, right? You could probably figure out the molecular formula for this thing, right? And we just started this, so you guys are really doing really good, okay? So, again, let's erase these just so we don't think that all bond line structures have those. Sometimes when you want to emphasize the hydrogen, they'll show it, you know? But not always, okay? So, before we all leave, how many hydrogens are on that one? Zero. Why? Why? One, two, three, four. How many on that one? One. One. How many on that one? Nine. Zero. Very good, nine. Zero. Zero. This one? One. One. Zero. Zero. This one? Two. Two. Two. Remember, I like to show my long hairs just so I can remember to keep track of all my electrons. So, all of these, all of the atoms in these molecules that aren't hydrogen, remember, have eight electrons around them. If they don't, they'll be charged, okay? So, we have a positive or a negative charge, okay? Is everybody cool with that? Oh, yeah. Okay, have a good weekend. You too.