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Atomic Structure: Valence Electrons and the Periodic Table - Tyler Dewitt

Added Oct 18, 2017 •

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in the next couple minutes we're going to talk a lot about electrons first we're going to start out looking at an atom and looking at the spaces in an atom where electrons can live then we'll learn about the most important type of electron these are called the valence electrons will learn how you can figure out how many valence electrons an atom has by looking at where that Adam is on the periodic table and finally we'll look at how you can Adam and draw one of these electron dot diagrams for that shows how many electrons it has so let's get started okay so check out this diagram of an atom I have here in a middle is the nucleus protons and look at all these little circles each one of these circles represents a spot that could hold one electron you can think of these as like parking spots for electronics more like fear seats for electrons and these spots for electrons are organized into these circles the circles are called energy levels or shells you can think of these energy levels or shells sort of like they show the path that the electrons would take as they're spinning around the nucleus here but also energy levels or shells range electrons in 10 different groups that are varying distances from the center that okay like show for this first group the first energy level or shell can hold two electrons cinequest moving out a little bit we get to another shell that can hold 8 electrons and they're spinning out here and then even further out we have another group that can hold 8 electrons it keeps going from here and there are more and more energy levels or but it gets a little bit tricky so I just wanted to focus on these first three to give you an idea of how they work now if you've learned a little bit about atoms already you might know the way I've drawn this here this isn't the most perfectly accurate way to represent electrons in atoms but you know what it doesn't matter for our purposes right now we just want to learn the basics drawing and thinking about atoms like this is totally fine so don't worry that it's not super accurate let's look at what happens when we start filling these electrons parking spaces when we start filling them with actual electrons so we're going to use the periodic table for This Will Go On by call and here's what I'm doing made this big version of a periodic table needed to looks a little bit different than the real version of a periodic table okay look at this whole thing in the middle this is sort of a periodic table going to worry about any of these elements in here in the middle so this whole section I've put it here just gotten rid of it we're not going to worry about it we're only going to focus on eight columns are going to focus on these two right here which I've drawn their skipping every and then we're going to focus on V6 over here so don't get confused by the way I've drawn this we're just leaving out some of the elements that we don't want to get into right now so let's take the first element right here hydrogen now how many electrons are there in hydrogen okay what we got to look it up on the periodic table and we're going to find something like this now the periodic table it doesn't actually how many electrons are in hydrogen I'm here but that refers to the number of protons there's one proton in Hydra that's what it's atomic number is now if we assume though that this hydrogen atom if we assume it doesn't have a charge then the number of electrons is going to equal the number of protons to hydrant always has one proton but if the atom is neutral if it doesn't have a charge it will also have one electric so let's go back to this diagram of the eye let's just start with this first energy level okay here's a drawing just in the first energy level let's put a nucleus in here I'm not actually going to draw the protons and neutrons instead of just going to write the number of protons okay so this has one proton and P plus a zebra the one p plus in the nucleus now here are the two spots in the first energy level where electrons can live there is one electron of hydrogen forgot to fill that in that was really easy right energy level and hydrogen one of the spots is still empty and one of the spouses full let's move down here to lithium lithium on the periodic table we're going to see the 3 which means that every lithium atom has 3 protons in it but if that lithium atom is neutral which we always assume that is one or two that sort of thing does lithium also has 3 electrons will start here will be first cancer and with this at this energy level that's right here the first one here I'm inputting nucleus in here 3 + p+ because they're three protons in here okay so they're three electrons so this one's going to get filled and this one is going to get filled and we're going to go out want to go to the next energy level okay now that starts getting felt so now it's going to look like this now we want to start thinking about the second energy level the first one is filled and now one electron is going to go here in the SEC so these energy levels there really like parking spaces imagine the nucleus is a mall right it's like the parking space is closest to the entrance of the mall those are the ones that fill out first and that is or more people Park the empty parking spaces moved further and further and further away from the center of the mall it's exactly the same way with Adams okay the first energy levels close to the new Chris those the ones that are going to fill up and then after their fault the other energy levels further out they are going to begin to fill up to okay now let's look at the sodium sodium has 11 protons in its nucleus people ever going to assume that since it's neutral were assuming that it's neutral it has the same number of electrons and protons so let's start filling them at 1:20 in the first energy level now that's. We're going to start filling the second energy level three four five six seven eight nine 10 and finally bees are all full but we still have more electrons than are going to have to bump it to the third energy level here's a third energy level we can start filling in head of these are already winning the atoms are going to add one more and now there's one in this third energy level okay now check this out because this is worked hydrogen lithium and sodium they all have different numbers of electrons there's a pattern here check this out each one of these atoms has one electron in the outermost shell okay this one's for this one's full but then there is just one here this one's full and then there's just one here and hydrant he only has one energy level and it just has one electron it these electrons 1001 are the valence electrons the most important electrons in an atom will talk more about that why they're so important but you have to know for right now is it the valence electrons are the electrons in the energy level that is the furthest out from the nucleus so in this atom the Veil energy level is the third and it has one electron in here the valence energy level that the furthest out is the second and hear the farthest out of valence energy level is the first so there's a pattern which one of these atoms has one valence electron that's true not just for these first three items but for every one of the atoms that's in this first column in the periodic table I didn't want to do it electron structures for all of these others but just trust me that they all have one Electra okay so now there's a way that we want to be able to write that to show that these elements have one valence electron don't we can do is grow up what we call these electron dot diagrams are sometimes known as Lewis diagrams where we take the element and then put one daughter over it to show that it has one valence electron here's how we write the electron dot diagrams for all the elements that are in this column as an example I'll just take a lithium and write it here so every single atom in this call has one valence electron let's move on and take a look at some of the other columns on a periodic table okay so if everything here has one valence electron let's take a look at this call beryllium really has 4 protons electrically neutral it's going to have four electrons as well so let's look at how this feels in we've got four protons here in the nucleus and now we're going to go 1-2 in the first energy level in the second energy level three four Okay so we've got two electrons in the outer energy level and look at the way I feel them and I didn't just fill them in clock was here but one on the top and then one went on the bottom now magnesium magnesium here has an atomic number of 12 to 12 protons and 12 electrons if we assume that it is electrically neutral 12 p + 12 1/2 three four five six seven eight nine 10 11 12 so what's the pattern here for this second column in the periodic we've got two valence electrons for magnesium in the third energy level and we have two valence electrons for beryllium in the second energy level so everything in this column has two valence electrons in the outermost shell so we can do is we can draw electron diagrams for everything in the second shell here I'm sorry for everything the second column here and it looks like this we take the element symbol and they reported at the top and a. At the bottom and that's how we represent the electrons for here so I'll just do like really in for an example to be dot on the top. On the bottom what's going on okay you're probably getting the hang of this so we're going to start moving a little bit faster let's move on to Boron here here's Boron this is the structure of boron and then here is aluminum down here 13 proton 5 * 5 protons 13 protons and look at what the structure of the valence electrons is here we got 1 2 3 in the valence shell of boron and for aluminum we've got 1 2 3 in the valence shell trophy these guys here even though I haven't run them out so if in your if you're in this column you have three valence electrons an example of this would be Boron and look at how I do that for Boron okay I do a DOT on the top just what am I doing. On the bottom just like beryllium and then I do a DOT here to the left to show that these all have three valence electrons and it would be the same way for any of the elements in this column here okay let's do all of these as a group okay just call him first has carbon and silicon have 1 2 3 4 1 2 3 4 valence electrons in their outer shell okay so I can take this and do a Don appear a. Down here adopt to the left and then I. To the right to show the everything in this column has four Alexis no moving on to the right and phosphorus and all these others and everything here has one two three four five one two three four five bounce electrons so if a nitrogen is my example going to do end. On the top down on the bottom left right and now I start doubling up so now they're going to be two dots on the top of nitrogen to show that there are these five valence electrons for everything that's in this car you can probably see there's a pattern developing here oxygen and sulfur each have you can count them 6 I'll take oxygen as an example now look at what I do here for drawing the valence electrons because it gets a little bit tricky you'll figure out that it's really okay. So anyways six valence electrons for everything in this call oxygen example. down on the bottom. On the left. On the right now we double up the one on the top and then we double up the one on the right okay so we don't put it on the bottom we put it on the right so up down left right and then around clockwise finally for this column which has at the top of it fluorine and chlorine have 7 valence electrons which means in this valence shell is almost except for one hole in it so pick fluorine is mining example here. On the top. On the bottom. On the left. On the right now we double up double up on the top two double up on the right and then double up on the bottom so I've only got one guy here on the left that doesn't have a pair of here's the last column that we're going to talk about OK Google what happens here will look at Helium neon and argon okay here's helium neon and here is our God notice the Argon has 8 valence electrons doesn't have any empty holes in space neon also has 8 valence electrons but helium only has two valence electrons okay so what's going on in this call is that most of these have neon has a argon has 8 as do Krypton Xenon and radon but then there's healing that only has two but regardless of whether you have to buy mirror of whether you had eight or whether you have to if you were in this call your valence shell is totally full okay so here's for they hear it's for they and here it's full with two but they're all full and there aren't any holes in the shells so is an example I'm going to use neon which has 8 so 1 2 3 4 and now we go clockwise 5 6 7 8 eight valence electrons for most of these guys but remember that helium only has two valence electrons but that all of them have valence shells that are totally full with no empty spots just kind of sums up everything talk about every atom in this column has one valence electron every atom in this column has two valence electrons and then we skip over this middle section and we get 3 4 5 6 7 and 8 so if you know which of these columns a particular atom is in you can figure out how many valence electrons

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Atomic Structure: Valence Electrons and the Periodic Table - Tyler Dewitt

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