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I get the same number of moles. Divide, and I get my molarity. Okay? Number two, it's a little bit trickier. Okay? Okay? Alright, I'm just going to stop here for a second. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Number two, it's a little bit trickier. Okay? Okay? Alright, I'm just going to stop here for a second. Okay? This is not the end of the problem. But I want to just make sure some things are clear. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Alright, I'm just going to stop here for a second. Okay? This is not the end of the problem. But I want to just make sure some things are clear. Okay? First of all, this is the net ionic equation because it was strong acid plus strong base. Okay? | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
But I want to just make sure some things are clear. Okay? First of all, this is the net ionic equation because it was strong acid plus strong base. Okay? Then, in the problem, I was given molarities and volumes, one for the acid and one for the base. Multiply them, you get moles of the acid, moles of the base. Why is t... | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Okay? Then, in the problem, I was given molarities and volumes, one for the acid and one for the base. Multiply them, you get moles of the acid, moles of the base. Why is this step necessary? We talked about this last class. Why do I have to do that? Why don't I tell you? | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Why is this step necessary? We talked about this last class. Why do I have to do that? Why don't I tell you? Oh, Evan. Right. Right. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Why don't I tell you? Oh, Evan. Right. Right. This given information, I've got to get it into units of something that is in my net ionic equation, which is the ions. And that's where that two comes in. Alright? | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Right. This given information, I've got to get it into units of something that is in my net ionic equation, which is the ions. And that's where that two comes in. Alright? Now, from this point, think about what you have. You have amounts of both of your reactants. What situation is this? | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Alright? Now, from this point, think about what you have. You have amounts of both of your reactants. What situation is this? Limiting reactant situation. Well, listen. We're being asked to figure something out about the excess reactant. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
What situation is this? Limiting reactant situation. Well, listen. We're being asked to figure something out about the excess reactant. Before I answer that question, can you tell me which one is the limiting reactant? How do you know that? Okay. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
We're being asked to figure something out about the excess reactant. Before I answer that question, can you tell me which one is the limiting reactant? How do you know that? Okay. Now, I want you guys to be very, very careful with this one. What Alan said is correct. This is the limiting reactant. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Okay. Now, I want you guys to be very, very careful with this one. What Alan said is correct. This is the limiting reactant. How did you know? Because there's less of it. Now, the only reason he can use that argument is because the reactants are in a one-to-one ratio. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
This is the limiting reactant. How did you know? Because there's less of it. Now, the only reason he can use that argument is because the reactants are in a one-to-one ratio. If they were not, if there was like a three coefficient and a four there, you can't just look at them like that. Usually what you have to do in a... | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Now, the only reason he can use that argument is because the reactants are in a one-to-one ratio. If they were not, if there was like a three coefficient and a four there, you can't just look at them like that. Usually what you have to do in a limiting reactant problem is turn each reactant into some amount of product ... | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
The only reason I don't have to do that in this problem is because everything's one-to-one-to-one. Okay? So, let me write it down. Limiting, what's the opposite of limiting? Excess. So, this is the one I care about. Here's the next question to you. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
Limiting, what's the opposite of limiting? Excess. So, this is the one I care about. Here's the next question to you. You are asked, what is the concentration of hydroxide that is left over? That's not what this is. This is the amount of hydroxide I have at the beginning of the reaction. | Chapter 4 (Types of Chemical Reactions and Solution Stoichiometry) - Part 3_segment1.mp3 |
In this video, we're just going to do a few more examples of five electron clouds. So let's say we wanted to find the shape of chlorine trifluoride. We start by drawing a dot structure, which means we have to figure out the valence electrons. So for chlorine in group 7, therefore 7 valence electrons. Fluorine is in gro... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So for chlorine in group 7, therefore 7 valence electrons. Fluorine is in group 7. And we have 3 fluorines. So 7 times 3 is 21. Plus 7 means we have a total of 28 valence electrons that we need to show in our dot structure. Chlorine is going to go in the center, since it is not as electronegative as fluorine. And we kn... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So 7 times 3 is 21. Plus 7 means we have a total of 28 valence electrons that we need to show in our dot structure. Chlorine is going to go in the center, since it is not as electronegative as fluorine. And we know that the chlorine is bonded to 3 fluorines. So we can go ahead and put in our 3 fluorines in here like th... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And we know that the chlorine is bonded to 3 fluorines. So we can go ahead and put in our 3 fluorines in here like that. We have represented 2, 4, and 6 valence electrons so far. So 28 minus 6 means we have 22 valence electrons left. And we know we start by putting those leftover valence electrons on our terminal atoms... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So 28 minus 6 means we have 22 valence electrons left. And we know we start by putting those leftover valence electrons on our terminal atoms, which are our fluorines. Fluorine is going to follow the octet rule. And each fluorine already has 2 electrons around it. And so therefore, each fluorine needs 6 more. So when w... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And each fluorine already has 2 electrons around it. And so therefore, each fluorine needs 6 more. So when we put 6 more valence electrons around each fluorine, now each fluorine has an octet. We just represented 6 times 3 more valence electrons. So 6 times 3 is 18. And 22 minus 18 is 4. So we're left with 4 valence el... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
We just represented 6 times 3 more valence electrons. So 6 times 3 is 18. And 22 minus 18 is 4. So we're left with 4 valence electrons. And when you have leftover valence electrons after assigning them to your terminal atoms, you're going to give them to your central atoms. So we're going to assign 4 valence electrons ... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So we're left with 4 valence electrons. And when you have leftover valence electrons after assigning them to your terminal atoms, you're going to give them to your central atoms. So we're going to assign 4 valence electrons to our central atom. And it makes sense to put those in lone pairs. So there's one lone pair. An... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And it makes sense to put those in lone pairs. So there's one lone pair. And there's another lone pair on the chlorine. And so now that takes care of all of our valence electrons. In terms of looking at the dot structure and thinking about chlorine there, it actually is exceeding the octet rule. And that's OK for chlor... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And so now that takes care of all of our valence electrons. In terms of looking at the dot structure and thinking about chlorine there, it actually is exceeding the octet rule. And that's OK for chlorine to exceed the octet rule because of its position in the third period on the periodic table. I like to think about fo... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
I like to think about formal charge. So if you actually assign a formal charge to that chlorine, you'll see it has a formal charge of 0, which to me just helps me understand these dot structures a little bit more. And so we've drawn a dot structure that makes sense. And so we can move on now to the second step, which i... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And so we can move on now to the second step, which is where we count the number of electron clouds that surround our central atom. So remember, electron clouds are regions of electron density, which means that bonding and non-bonding electrons would fit into that category. So here we have a bonding pair of electrons o... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
Here's another bonding pair of electrons in an electron cloud. Here's another one. And then we have our lone pairs of electrons. Our non-bonding electrons are still regions of electron density. And so there is an electron cloud. And then our last lone pair there. So a total of five electron clouds surrounding our centr... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
Our non-bonding electrons are still regions of electron density. And so there is an electron cloud. And then our last lone pair there. So a total of five electron clouds surrounding our central atom. In step three, predict the geometry of those electron clouds around your central atom. And in the previous video, we use... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So a total of five electron clouds surrounding our central atom. In step three, predict the geometry of those electron clouds around your central atom. And in the previous video, we used VSEPR theory to talk about why five electron clouds are going to form a trigonal bipyramidal geometry. So they're going to repel each... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So they're going to repel each other as much as they possibly can. Turns out that's a trigonal bipyramidal geometry here. So our electron clouds are going to be in the same geometry here. So the only tricky part for this dot structure is where do you put your lone pairs of electrons? Lone pairs of electrons take up mor... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So the only tricky part for this dot structure is where do you put your lone pairs of electrons? Lone pairs of electrons take up more space. These non-bonding lone pairs of electrons take up more space than bonding electrons. And therefore, they repel more. So where you put them is extremely important for the overall s... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And therefore, they repel more. So where you put them is extremely important for the overall structure of the molecule. In the last video, we talked in a lot of detail about the fact that you're going to put non-bonding electrons or lone pairs of electrons in the equatorial position to minimize electron pair repulsion.... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And so we're going to do the same thing here. We're going to put our lone pairs of electrons equatorial. So let me go ahead and put in my central chlorine atom. I'm going to put a lone pair of electrons in equatorial here. And then the other lone pair of electrons also equatorial right here. And that means that I have ... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
I'm going to put a lone pair of electrons in equatorial here. And then the other lone pair of electrons also equatorial right here. And that means that I have one more spot. I'm going to put one of the fluorines in the last equatorial position. And so that leaves two more fluorines, which we're going to put axial. So o... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
I'm going to put one of the fluorines in the last equatorial position. And so that leaves two more fluorines, which we're going to put axial. So one fluorine axial here and one fluorine axial here. Again, putting your lone pairs equatorial minimizes electron pair repulsion. And watch the previous video for more details... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
Again, putting your lone pairs equatorial minimizes electron pair repulsion. And watch the previous video for more details about that. This is actually a more complicated example than what I talked about in the previous video. But the same ideas apply here as well. I could probably spend a whole video talking about jus... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
But the same ideas apply here as well. I could probably spend a whole video talking about just this one molecule. But we don't really have time for that. So when you're talking about five electron clouds, just think about putting your lone pairs in the equatorial position. And so now we have the general structure here.... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So when you're talking about five electron clouds, just think about putting your lone pairs in the equatorial position. And so now we have the general structure here. Let's go ahead and talk about the final shape. So when you're talking about the final shape, you ignore any lone pairs and you predict the geometry of th... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So when you're talking about the final shape, you ignore any lone pairs and you predict the geometry of the molecule here. So if we ignore lone pairs, let me go ahead and redraw that. So we're going to go ahead and put in our chlorine here. So there's our chlorine. We ignore lone pairs. So we have our two axial fluorin... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So there's our chlorine. We ignore lone pairs. So we have our two axial fluorines. And then we have our equatorial fluorine, 90 degrees to our axial fluorines. And so that's, of course, an ideal bond angle. So let's talk about the bond angles here. So if you look at the shape, it looks kind of like these are linear her... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And then we have our equatorial fluorine, 90 degrees to our axial fluorines. And so that's, of course, an ideal bond angle. So let's talk about the bond angles here. So if you look at the shape, it looks kind of like these are linear here. And then this is 90 degrees to that. So you can see kind of a T shape here. And ... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So if you look at the shape, it looks kind of like these are linear here. And then this is 90 degrees to that. So you can see kind of a T shape here. And so we actually call this molecule the shape T-shaped, because we're ignoring the lone pair of electrons. And so we see a T shape right here. So this is a T-shaped geo... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And so we actually call this molecule the shape T-shaped, because we're ignoring the lone pair of electrons. And so we see a T shape right here. So this is a T-shaped geometry. In terms of the ideal bond angle, since it is T-shaped, it makes it simple. So you can think about for your bond angles, this one you would exp... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
In terms of the ideal bond angle, since it is T-shaped, it makes it simple. So you can think about for your bond angles, this one you would expect to find a 90 degree bond angle for the fluorine, chlorine, fluorine bond angle here, and then 180 degrees on this side. But once again, those are just ideal bond angles. Tha... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
That's what you would predict thinking about a simple T shape. The actual bond angles you would have to get experimentally. So a T-shaped geometry here. All right, let's do one more example of five electron clouds. So this is the triiodide ion. So I3 with a negative charge here. So we need to draw the dot structure. | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
All right, let's do one more example of five electron clouds. So this is the triiodide ion. So I3 with a negative charge here. So we need to draw the dot structure. So we need valence electrons. Iodine's in group 7. So 7 times 3 gives us 21 valence electrons. | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So we need to draw the dot structure. So we need valence electrons. Iodine's in group 7. So 7 times 3 gives us 21 valence electrons. But this is an ion, so it has a negative charge. It has an extra electron. So we have to add one to that. | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So 7 times 3 gives us 21 valence electrons. But this is an ion, so it has a negative charge. It has an extra electron. So we have to add one to that. So 21 plus 1 gives us a total of 22 valence electrons to show in our dot structure. So we have three iodines. We can go ahead and show our three iodines bonded together l... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So we have to add one to that. So 21 plus 1 gives us a total of 22 valence electrons to show in our dot structure. So we have three iodines. We can go ahead and show our three iodines bonded together like that. And we've already represented four valence electrons. So two here and two here. So 22 minus 4 means we have 1... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
We can go ahead and show our three iodines bonded together like that. And we've already represented four valence electrons. So two here and two here. So 22 minus 4 means we have 18 valence electrons left. And we start by putting those leftover valence electrons on our terminal atoms, which are our iodines. So we're goi... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So 22 minus 4 means we have 18 valence electrons left. And we start by putting those leftover valence electrons on our terminal atoms, which are our iodines. So we're going to think about our terminal atoms as following the octet rule here. And so we're going to put six more electrons on each iodine to give each iodine... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And so we're going to put six more electrons on each iodine to give each iodine an octet. And so I just represented 12 more valence electrons. So 18 minus 12 gives us six valence electrons left over. And those leftover electrons are, of course, going to be assigned to our central atom. And so with six valence electrons... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And those leftover electrons are, of course, going to be assigned to our central atom. And so with six valence electrons, you would expect three lone pairs of electrons. So let's go ahead and put those last six valence electrons around our central iodine in the form of three lone pairs. And since this is an ion, we sho... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And since this is an ion, we should put this in brackets and put a negative 1 charge outside like that. So this is our dot structure. And if we look at our central iodine, it's once again exceeding our octet. So it's once again OK for iodine to expand its valence shell because of its position on the periodic table. And... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So it's once again OK for iodine to expand its valence shell because of its position on the periodic table. And if you assign a formal charge to that iodine, you'll see it's a negative 1 formal charge, which once again I always like to do just to help me understand what's going on a little bit better here. So this is a... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And so let's go back up here to our next step. So number one, we've already drawn a dot structure to show our valence electrons. In step two, we count the number of electron clouds that surround our central atom. So let's go ahead and look at our central atom and figure out how many electron clouds surround it. So thes... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So let's go ahead and look at our central atom and figure out how many electron clouds surround it. So these bonding electrons are an electron cloud. These bonding electrons are an electron cloud. And our non-bonding electrons, our lone pairs of electrons, are still regions of electron density. And so you can see we ha... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And our non-bonding electrons, our lone pairs of electrons, are still regions of electron density. And so you can see we have a total of five electron clouds for this dot structure too. So for five electron clouds, that's going to be a trigonal bipyramidal arrangement of our electron clouds around our central atom. So ... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So go ahead and put in our central atom here. We think about our electron clouds being in a trigonal bipyramidal arrangement. And we have seen that we put lone pairs of electrons into the equatorial positions to minimize electron pair repulsion. So we have three lone pairs of electrons that surround our central iodine.... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So we have three lone pairs of electrons that surround our central iodine. So we're going to put those three lone pairs equatorial. So we have our three lone pairs of electrons equatorial like that. And then we still have two iodines. And so one iodine would have to go axial up here. The same thing for the other iodine... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And then we still have two iodines. And so one iodine would have to go axial up here. The same thing for the other iodine down here. And so I'll just leave off the lone pairs of electrons. And so this is what our ion looks like. Let's go back up here to our steps. And let's look at, let's see, we've already done step t... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And so I'll just leave off the lone pairs of electrons. And so this is what our ion looks like. Let's go back up here to our steps. And let's look at, let's see, we've already done step three. We predicted the geometry of the electron clouds to be trigonal bipyramidal. But when you're trying to predict the geometry of,... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And let's look at, let's see, we've already done step three. We predicted the geometry of the electron clouds to be trigonal bipyramidal. But when you're trying to predict the geometry of, in this case, the ion, you ignore any lone pairs of electrons. Let's go back down and look at it again. So we're going to ignore th... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
Let's go back down and look at it again. So we're going to ignore the lone pairs of electrons around the central atom. And when we do that, we look for the shape. And we can see the shape is just a straight line. So we say it's a linear shape. So this is a linear shape. And since it's linear, we would predict the bond ... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
And we can see the shape is just a straight line. So we say it's a linear shape. So this is a linear shape. And since it's linear, we would predict the bond angle to be approximately 180 degrees since it's a straight line. And so that's the way to approach drawing this dot structure. And so we've done four examples of ... | VSEPR for 5 electron clouds (part 2) AP Chemistry Khan Academy (2).mp3 |
So nitrogen has an atomic number of 7 and an average atomic mass of 14.01. So an atom of nitrogen has 7 protons and 7 electrons. Electrons are electrically neutral. Now let's draw a simple Bohr model of the nitrogen atom. In the first shell, or the first energy level, nitrogen carries 2 electrons. That's the maximum nu... | Valence Electrons and the Periodic Table.mp3 |
Now let's draw a simple Bohr model of the nitrogen atom. In the first shell, or the first energy level, nitrogen carries 2 electrons. That's the maximum number of electrons you can have in the first energy level. In the second energy level, you can have up to 8 electrons, but what we have is a total of 7. So we need to... | Valence Electrons and the Periodic Table.mp3 |
In the second energy level, you can have up to 8 electrons, but what we have is a total of 7. So we need to place 5 in the second energy level so we can have a total of 7. The valence electrons are the electrons in the outermost energy level. So therefore, nitrogen has 5 valence electrons. So here are the 5 valence ele... | Valence Electrons and the Periodic Table.mp3 |
So therefore, nitrogen has 5 valence electrons. So here are the 5 valence electrons of the nitrogen atom. Now the inner shell electrons, the ones on the inside, the ones that are not valence electrons, these are known as core electrons. So nitrogen contains 2 core electrons for a total of 7 electrons, which goes with t... | Valence Electrons and the Periodic Table.mp3 |
So nitrogen contains 2 core electrons for a total of 7 electrons, which goes with the atomic number of nitrogen. Now keep in mind, for atoms, the number of protons and electrons are the same, but for ions, they differ. So you have to adjust it based on the charge. Now let's look at another example. Let's consider the a... | Valence Electrons and the Periodic Table.mp3 |
Now let's look at another example. Let's consider the aluminum atom, which has an atomic number of 13 and an average atomic mass of 26.98. How many valence electrons and core electrons can be found in the aluminum atom? So let's draw a picture. So this is going to be the first shell, this is the second energy level, an... | Valence Electrons and the Periodic Table.mp3 |
So let's draw a picture. So this is going to be the first shell, this is the second energy level, and this one is going to be the third. So in the first energy level, there's going to be 2 electrons. Now we said the second can hold a maximum of 8 electrons. So right now we have a total of 10, but we need to get up to 1... | Valence Electrons and the Periodic Table.mp3 |
Now we said the second can hold a maximum of 8 electrons. So right now we have a total of 10, but we need to get up to 13. So that's 13. So aluminum has 3 valence electrons. Those are the electrons in the highest energy level. Now how many core electrons does it have? It has 2 in the first shell, and then 8 in the seco... | Valence Electrons and the Periodic Table.mp3 |
So aluminum has 3 valence electrons. Those are the electrons in the highest energy level. Now how many core electrons does it have? It has 2 in the first shell, and then 8 in the second shell. So it has a total of 10 core electrons. If you add 10 plus 3, you're going to get the atomic number for the atom, 13 electrons ... | Valence Electrons and the Periodic Table.mp3 |
It has 2 in the first shell, and then 8 in the second shell. So it has a total of 10 core electrons. If you add 10 plus 3, you're going to get the atomic number for the atom, 13 electrons in total. So just make sure you understand this. The valence electrons are the electrons in the outermost energy level. These are th... | Valence Electrons and the Periodic Table.mp3 |
So just make sure you understand this. The valence electrons are the electrons in the outermost energy level. These are the electrons that participate in a chemical reaction. The inner core electrons, for the most part, rarely participate in a chemical reaction. It's the valence electrons that are involved in reactions... | Valence Electrons and the Periodic Table.mp3 |
The inner core electrons, for the most part, rarely participate in a chemical reaction. It's the valence electrons that are involved in reactions that we see in a day-to-day basis. Now another way in which you can identify the number of valence electrons is by writing the electron configuration. So let's write it for n... | Valence Electrons and the Periodic Table.mp3 |
So let's write it for nitrogen and for aluminum. The electron configuration for nitrogen, I'm assuming that you already know how to do this. If not, you can check out another video that I have on YouTube. It's 1s2 2s2 2p3. So notice that the exponents add up to 7 because nitrogen has a total of 7 electrons. Now in the ... | Valence Electrons and the Periodic Table.mp3 |
It's 1s2 2s2 2p3. So notice that the exponents add up to 7 because nitrogen has a total of 7 electrons. Now in the highest energy level, that's in the second energy level, we have two sub-levels, 2s and 2p. But in the second energy level, notice that we have a total of 5 electrons. So those 5 are the 5 valence electron... | Valence Electrons and the Periodic Table.mp3 |
But in the second energy level, notice that we have a total of 5 electrons. So those 5 are the 5 valence electrons. Those are the electrons in the outermost or the highest energy level. All the other electrons are known as core electrons. So you can see that nitrogen has two core electrons. Now let's consider aluminum.... | Valence Electrons and the Periodic Table.mp3 |
All the other electrons are known as core electrons. So you can see that nitrogen has two core electrons. Now let's consider aluminum. The electron configuration is 1s2 2s2 2p6 3s2 3p1. The s sub-level can only hold two electrons. p can hold up to 6 electrons and d can hold up to 10. But if we look at the highest energ... | Valence Electrons and the Periodic Table.mp3 |
The electron configuration is 1s2 2s2 2p6 3s2 3p1. The s sub-level can only hold two electrons. p can hold up to 6 electrons and d can hold up to 10. But if we look at the highest energy level of aluminum, which is the third energy level, we can see that there are 3 electrons there. 2 plus 1 is 3. So aluminum contains ... | Valence Electrons and the Periodic Table.mp3 |
But if we look at the highest energy level of aluminum, which is the third energy level, we can see that there are 3 electrons there. 2 plus 1 is 3. So aluminum contains 3 valence electrons. All the others represent core electrons. So we got 2 plus 2 plus 6. So aluminum contains 10 core electrons. So that's how you can... | Valence Electrons and the Periodic Table.mp3 |
All the others represent core electrons. So we got 2 plus 2 plus 6. So aluminum contains 10 core electrons. So that's how you can identify the number of valence electrons and core electrons using the electron configuration. Now let me give you another example. Let's use chlorine, which has an atomic number of 17. So in... | Valence Electrons and the Periodic Table.mp3 |
So that's how you can identify the number of valence electrons and core electrons using the electron configuration. Now let me give you another example. Let's use chlorine, which has an atomic number of 17. So in an atom of chlorine, write the electron configuration and then identify the number of core and valence elec... | Valence Electrons and the Periodic Table.mp3 |
So in an atom of chlorine, write the electron configuration and then identify the number of core and valence electrons. So the electron configuration of chlorine is 1s2 2s2 2p6 3s2 3p5. All the exponents add up to 17. So the valence electrons are the electrons in the highest energy level. So in the case of chlorine, we... | Valence Electrons and the Periodic Table.mp3 |
So the valence electrons are the electrons in the highest energy level. So in the case of chlorine, we have 2 plus 5, so 7 valence electrons. And the rest are core electrons. So we got a total of 10 core electrons. Another way in which you can identify the number of valence electrons is using the periodic table. You ca... | Valence Electrons and the Periodic Table.mp3 |
So we got a total of 10 core electrons. Another way in which you can identify the number of valence electrons is using the periodic table. You can identify it based on the group number of representative elements. So in group number 1, we have elements like hydrogen, lithium, sodium, potassium. These elements all have a... | Valence Electrons and the Periodic Table.mp3 |
So in group number 1, we have elements like hydrogen, lithium, sodium, potassium. These elements all have a valence electron of 1. They have 1 valence electron. Now in the second group, you have the alkaline earth metals like beryllium, magnesium, calcium. So these metals have 2 valence electrons. They're in group 2 of... | Valence Electrons and the Periodic Table.mp3 |
Now in the second group, you have the alkaline earth metals like beryllium, magnesium, calcium. So these metals have 2 valence electrons. They're in group 2 of the periodic table. Now we're going to skip the transition metals and move on to group 13, also known as group 3a. So these include aluminum, gallium, and I bel... | Valence Electrons and the Periodic Table.mp3 |
Now we're going to skip the transition metals and move on to group 13, also known as group 3a. So these include aluminum, gallium, and I believe indium is the next one. So these elements have 3 valence electrons. And I'm forgetting something. Can't forget about boron. After boron is aluminum, then we have gallium. So t... | Valence Electrons and the Periodic Table.mp3 |
And I'm forgetting something. Can't forget about boron. After boron is aluminum, then we have gallium. So these elements contain 3 valence electrons. Then after boron you have carbon, silicon, germanium. Those elements contain 4 valence electrons. Then you have nitrogen, phosphorus, and I believe arsenic. | Valence Electrons and the Periodic Table.mp3 |
So these elements contain 3 valence electrons. Then after boron you have carbon, silicon, germanium. Those elements contain 4 valence electrons. Then you have nitrogen, phosphorus, and I believe arsenic. So these, they're found in group 5a, so they contain 5 valence electrons. Then you have the calcogens like oxygen, s... | Valence Electrons and the Periodic Table.mp3 |
Then you have nitrogen, phosphorus, and I believe arsenic. So these, they're found in group 5a, so they contain 5 valence electrons. Then you have the calcogens like oxygen, sulfur, selenium. These guys, they hold up to 6 valence electrons. Then you have the halogens like fluorine, chlorine, bromine, iodine. Those guys... | Valence Electrons and the Periodic Table.mp3 |
These guys, they hold up to 6 valence electrons. Then you have the halogens like fluorine, chlorine, bromine, iodine. Those guys, they have 7. Now be careful with this one. Helium is a noble gas, but it only has 2 valence electrons because it has a total of 2 electrons. So it can't have 8. But the other ones after it l... | Valence Electrons and the Periodic Table.mp3 |
Now be careful with this one. Helium is a noble gas, but it only has 2 valence electrons because it has a total of 2 electrons. So it can't have 8. But the other ones after it like neon, I think it's argon, krypton, all of these, they have 8 valence electrons. Now I have another question for you. Let's focus on iodine,... | Valence Electrons and the Periodic Table.mp3 |
But the other ones after it like neon, I think it's argon, krypton, all of these, they have 8 valence electrons. Now I have another question for you. Let's focus on iodine, which has an atomic number of 53 and an average atomic mass of 126.9. Now how many core electrons are found in an atom of iodine? Think about it. N... | Valence Electrons and the Periodic Table.mp3 |
Now how many core electrons are found in an atom of iodine? Think about it. Now you can use any one of the techniques that we've illustrated in this video. You can draw the Bohr model of the atom, which is going to take time to draw 53 electrons. You can also write out the electron configuration, which works as well, b... | Valence Electrons and the Periodic Table.mp3 |
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