00:01
Hello, i am gonna work the first one of these to show you how to work the other two three four of them so first thing is first we want to go ahead and draw out the molecule i'm gonna draw two electrons here and black and the other two in red because they're gonna be moving for us they are gonna be moving down is what it looks like here and then we have the rest of the molecule and it looks like this is going to be moving to the carbon all right.
00:33
So now it's our job to draw the structure that it's turning into so the backbone has to stay the same with resonant structures what ends up happening is those two? those two electrons end up moving down on the oxygen to make a double bond here and the ones pointing at the carbon are gonna be sitting on the carbon here.
00:57
So that's all that's happening with a resonant structure the arrow is just causing these electrons to move now let's talk about formal charge so the formula for formal charge equals the number of valence electrons minus one half of shared electrons minus unshared electrons so first of all anything that has a carbon with four bonds is going to be a net charge of zero and the reason why is carbon sits in group 4a.
01:29
So there's four valence electrons minus one half.
01:32
Let's do this carbon for example anything that's not shown on a carbon on a lewis structure is assumed to be hydrogens on i'm sorry not a lewis structure on a stick structure is assumed to be hydrogens.
01:47
So ultimately every carbon should have four bonds and that means even if it's with hydrogens, that's eight electrons that's eight shared and that means there's zero unshared zero is only the dots on the outside of an atom and that's probably why the problem tells you to go ahead and draw all the dots so anyway, one half of eight is four and four minus four is zero so now that we've got all those out of the way what i want to do is the oxygens and these carbons right? underneath the oxygen and this carbon right here specifically so for oxygens, we'll do both of them at the same time.
02:28
It is going to be six valence electrons on both sides minus one half of shared there are two bonds here on that oxygen on the first structure.
02:39
So that is four electrons minus unshared which is the dots there are four dots this one over here one half of shared there are six shared because that bond moved and the number of unshared is two there's only two little dots so one half of four is two six minus two is four and four minus four is nothing one half of six over here is three six five four three two one...