Determine the formal change on atoms in NH4 plus. Before I can determine the formal charge, I must first have a Lewis structure for my molecule, and in order to draw the Lewis structure I must have the number of valence electrons. So, nitrogen has five valence electrons, plus four hydrogens, each with one valence electron, and because I have a plus charge which indicates the loss of an electron, I'm going to subtract one from that. And so what I see is that I have 8 electrons in my Lewis structure. Because that's the total number of valence electrons. So I draw my nitrogen in the middle, because hydrogen must be a terminal atom. And I'm going to draw everything with single bonds. Now I see that in my structure I've used up eight electrons, which is all the electrons I had. Draw my brackets and my plus sign just so I have a correct structure. And that's okay, because, remember, we don't need any additional electrons around hydrogen it only wants two, so it's perfectly fine that way. Now I want to look at my formal charges, so I'm going to look at my hydrogen first. I see that, in an isolated atom of hydrogen, that it would have one electron assigned to it. I'm going to subtract off the number of lone pair or lon, non-bonding electrons a sign to it in this structure which is zero and minus half of the bonding electrons. So I get a formal charge of 0, on each of my hydrogen atoms. Because they all have the same structure within this molecule. Now I'm going to look at my nitrogen. And I know that nitrogen has five electrons in the isolated atom. Here, it has no non-bonding electrons, and it has 8 electrons around it. So, half of eight equals four. So, five minus four is one. And so our nitrogen has a formal charge of plus one. And this is okay, because remember that the sum of our formal charges, must equal the sum of the charge on the particular substance. Here we have a plus one charge, so the sum of our formal charges should equal plus one. And we can't really get in any lower because we have to have that plus 1 charge. We do have lots of zeros, which indicates some stability in this structure. In general we're looking at formal charges, to compare whether something is a better structure than another. We have to have two different structures, and compare the sets of formal charges with each.