 So let's try one of these Lewis structure questions that goes to a polyatomic ion, you know. So what is this question? Draw the reaction showing the constituent elements to form the ammonium cation, polyatomic cation. So hopefully you remember what the formula for the ammonium cation is. If you don't, then, well, it would be hard to do this problem. But anyways, it's a polyatomic ion. Its formula is nH4+. Okay, so this is strange. This is different than the Lewis structures that we've seen before because the Lewis structures we saw before and that we built before didn't have that overall charge element. So you can add up all of your electrons and do it the way that the book shows you, but I'm going to show you another way to do it and I think it's a little bit easier. So the first thing I would have you do is draw out all of the different atoms that are in this structure. Okay, so you know already from the rules that the hydrogen atoms have to be on the periphery because they can only form one bond. So that means that the nitrogen has to be in the center. Okay, so let's just go about drawing that straight away, look something like this. Because these can only make one bond. So let's draw the normal Lewis structures of all of these atoms. Okay, so remember we're going to want to put one electron in the direction on each of these hydrogens in the direction towards the central atom. Nitrogen, since it's in group 15, has five valence electrons. So one, two, and we try to bond all these things together then we'll end up with nine electrons around that nitrogen and that's too many, okay? You can't have more than eight electrons around nitrogen. So anyways, what we can do to show that charge, right, what has happened, that means that something in this molecule or this molecule altogether has lost an electron. Okay, so what we'll do is we're going to just take the central atom and erase an electron from it causing us to have a nitrogen without one of its electrons. So something like an N plus, if you will. Okay, so when we do that we see nitrogen has space for all four of those hydrogen atoms. So let's go ahead, not squirming or the hands holding whatever you want to charge still on the nitrogen atom. Electrons just to see if everybody's got an octet. So hydrogen, remember only needs two electrons for an octet. Bonding electrons, it's got two. It's octet is built, right? So how many bonding electrons does it have? Two or four? Help me out with looking at it. The definition of these things, try one of those, you know, use reals from both, and it'll probably be the best way to go. Okay, cool. There's a polyatomic ion for you.