 Let's try this one for the first problem of the day. So this one is talking about the actual electron configuration of fluorine, so the atom fluorine. So what is the electron configuration of fluorine? So how do we do this? If you guys remember, so it's just that 1s, 2s stuff. So you just got to look at the periodic table. So remember, the periodic table, it's like your cheat sheet. So remember, you'll always have it available to you, so it's really cool. If you learn how to use it, a lot of your chemistry problems will be solved just by looking up at it. So it really does come in handy. But anyways, this will be one of the first problems that we talked about in relation to that. But anyways, so if you look where fluorine is, so it's group 7 or 7 and 8 or 17. All of those are correct names for that group. So it's the second from the right, and remember, we call those the halogens if you recall the common name of those. So it's in the group known as the halogens. And they're fairly common for you to see in introductory or general chemistry. So I'd go ahead and learn about them. So this is a good problem to understand because it really applies to not just fluorine, but chlorine, bromine, and iodine, too. But anyways, for some parts that is. But anyways, so what is the electron configuration of fluorine? So it's this group 7, and you can see it's period 2 or row 2. So remember row and period are the same thing, but periodic tables that we call periods. So it's all the way almost to the end there. So if you recall, period 1 is where you get the electron configuration designated as 1, and the s is the first orbital set of orbitals that's going to be filled. And remember, if you count from the periodic table, like hydrogen, helium, right? So there's two of them, so you put a 2 there, right? So then you go to the next period, and then that's going to be 2. And remember, s orbital is the first one that's filled, so 2s. And then you look, lithium, beryllium are the first two elements on that period. So 2. So in fact, this would be the electron configuration for beryllium. And then you go on to the next portion of the periodic table, which is the p-block remember, so 2p, 2 because we're still in that same period or same row, p because we're in the p-block. And remember, the periodic table is set up to show you how many electrons can fit into those orbitals. So if you look, it's, right, six electrons, but fluorine is only the fifth one there. So you count 1, 2, 3, 4, 5, right, put a 5 there, okay? So that's the full electron configuration of fluorine, or the electron configuration of fluorine. So how many valence electrons does fluorine have? Well, for valence electrons, right, you just look at the last period because it's the last shell of electrons or the last energy level of electrons. So if we look here, right, there's seven valence electrons, right, 2 plus 5 is seven. So fluorine has seven valence electrons. And you can represent that later, you'll learn about this. You represent this as what's known as Lewis structure. So fluorine with its elemental symbol there, and then you draw its electrons as little dots. And you can see those seven valence electrons. And in fact, in a second, we'll learn that atoms are what will be known as ions when, in the case of fluorine, have their octet filled or have eight electrons. But anyway, so what is the energy level of these electrons? Well, again, the energy level is what period they're on. So the energy level here is 2. In fact, a lot of times we'll designate that as what's the total number of electrons in fluorine? Well, if you can do your full electron configuration, count up that number. So valence electrons, total number of electrons will be 2, 4, 4 plus 5 is 9. So let's put that minus as a common question. The valence electrons, so the other two electrons, helium, are very condensed here. But when you're down, because you don't have to write, you'll know what I'm talking about later. OK, cool.