00:01
To calculate a formal charge on a specific atom, you're going to take the number of valence electrons that it contains, and then you're going to subtract it from the number of non -bonding electrons, and then add this to the number of bonds.
00:15
And so you can see here on the pr table, i have the number of valence electrons listed, and so we can use this to calculate the formal charge.
00:26
So let's go ahead and start with this hydrogen atom on our first example.
00:30
And so when we're calculating this, our number of valence electrons of hydrogen based on the pair table is one.
00:37
And then we are going to subtract this to the number of non -bony electrons.
00:43
And you'll see, if you'll see here, there is not any one pairs or non -bonding electrons.
00:48
So we will put zero.
00:49
And then you can add this to the number of bonds it has.
00:53
And it only has one bond to carbon.
00:56
And so we can put one, which gives us a total of a zero charge.
01:01
And so looking at our next atom carbon, for this middle one, you'll notice that it has four valence electrons based on the periodic table.
01:09
And then it has no non -bonding electrons.
01:15
And so we can put zero.
01:17
And then we add this to our number of bonds it has, which is four.
01:20
So one bond right here, and then a triple bond on the right side.
01:25
And so our total number of bonds is four.
01:28
And so this gives us another charge of zero.
01:30
And so now looking at our last carbon on the right side, you will notice that there is a lone pair, so we have to keep that in mind.
01:38
And so it has four valence electrons as found on the pr table, and then it has two non -bonding electrons.
01:47
And so we have to consider each one of these.
01:50
And so we have two non -bonding electrons, and then we have a total of three bonds.
01:57
So this is how we get our charge of negative 1.
02:01
And if we add up all these charges, we will get negative 1, which is shown here because the total of all of them should be negative 1.
02:11
So this is how you can check to see if your formal charges on each atom are correct.
02:17
And so here we know that they are because the total was negative 1.
02:21
So now let's go ahead and move on to our second one.
02:24
And this one, make sure you label all your atoms if you have same atoms and, you know, one structure.
02:32
And so because i had three different oxygen atoms, i went ahead and labeled them separately and numbered them like this.
02:38
And so also notice the two minus charge.
02:41
So the sum of all of our charges should be negative too.
02:44
And so we should be able to find that calculating the formal charges.
02:48
And so for our first oxygen atom, looking at the periodic table, we see that we have a total of six valence electrons.
02:57
And then we can subtract this from our number of non -bonding electrons, which is six.
03:03
Because you see here, we have a lone pair, a lone pair, and a lone pair, and all of these add up to six non -bonding electrons.
03:13
And then next, we add this to our number of bonds, and we only have one bond right here...