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On either side, I have a bunch of water molecules on either side, so I have a lot of water molecules. I just had water molecules here. They're all bouncing around in random directions. And so the odds of a water molecule going this way equivalent to odds of a water molecule going that way, assuming that both sides have... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And so the odds of a water molecule going this way equivalent to odds of a water molecule going that way, assuming that both sides have the same level of water molecule, otherwise the pressures would be different. So let's say that the top of this is the same as the top of this. So there's no more pressure going in one... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So if for whatever reason a bunch more water molecules were going in the rightward direction, then all of a sudden this would fill up with more water, and we know that that isn't likely to occur. So this is just a solution, or this is just two containers of water. Now let's put some solute in it. Let's dissolve some so... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Let's dissolve some solute in it. Let's say we do all the dissolving on the left-hand side, so we put some sugar molecules on the left-hand side, and these are small enough to fit through this little pipe. That's one assumption that I'm making. So what's going to happen? All of these things have some type of kinetic en... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So what's going to happen? All of these things have some type of kinetic energy. They're all bouncing around. Well, over time, the water is going back and forth. This water molecule might go that way, that water molecule might go that way, but they net each other out. But over time, one of these big sugar molecules wil... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Well, over time, the water is going back and forth. This water molecule might go that way, that water molecule might go that way, but they net each other out. But over time, one of these big sugar molecules will be going in just the right direction to go through, maybe this guy, instead of going in that direction, he s... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
He goes just through this tunnel connecting the two containers, and he'll end up there. And this guy will still be bouncing around. There's some probability he goes back, but there's still more sugar particles here than there. So still there's more probability that one of these guys will go to that side, than one of th... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So still there's more probability that one of these guys will go to that side, than one of these guys will go to that side. So you can imagine if you're doing this with gazillions of particles, I'm only doing it with four, over time, the particles will have spread out so that their concentrations are roughly equal. So ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But when you're only dealing with three or four or five particles, there's some probability it doesn't happen. But when you're doing it with a gazillion and they're super small, it's a very, very, very high likelihood. But anyway, this whole process, we went from a container of high concentration to a container of low ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And the particles would have spread from the low concentration container to the high concentration container. So they diffused. This is diffusion. And just so that we learn some other words that tend to be used with the idea of diffusion, when we started off, this had a higher concentration. The left-hand side containe... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And just so that we learn some other words that tend to be used with the idea of diffusion, when we started off, this had a higher concentration. The left-hand side container had higher concentration. It's all relative, right? It's only higher than this guy. Higher concentration. And this right here had a lower concent... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
It's only higher than this guy. Higher concentration. And this right here had a lower concentration. And there are words for these things. This solution with a high concentration is called a hypertonic solution. Let me write that in yellow. Hypertonic solution. | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And there are words for these things. This solution with a high concentration is called a hypertonic solution. Let me write that in yellow. Hypertonic solution. Hyper, in general, meaning having a lot of something, having too much of something. And this lower concentration is hypotonic. Lower concentration. | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Hypertonic solution. Hyper, in general, meaning having a lot of something, having too much of something. And this lower concentration is hypotonic. Lower concentration. You might have heard maybe one of your relatives, if they haven't had a meal in a while, say, I'm hypoglycemic. That means that they're feeling lighthe... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Lower concentration. You might have heard maybe one of your relatives, if they haven't had a meal in a while, say, I'm hypoglycemic. That means that they're feeling lightheaded. There's not enough sugar in their bloodstream and they want to pass out, so they want a meal. If you just had a candy bar, maybe you're hyperg... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
There's not enough sugar in their bloodstream and they want to pass out, so they want a meal. If you just had a candy bar, maybe you're hyperglycemic, or maybe you're just hyper in general. So these are just good prefixes to know. But hypertonic, you have a lot of the solute, so you have high concentration. And then in... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But hypertonic, you have a lot of the solute, so you have high concentration. And then in hypotonic, not too much of the solute, so you have a low concentration. These are good words to know. So in general, if there's no barriers to the diffusion, like we had here, you will have the solute go from a high concentration,... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So in general, if there's no barriers to the diffusion, like we had here, you will have the solute go from a high concentration, or hypertonic solution, if they can travel, to a hypotonic solution, to a hypo, where the concentration is lower. Now, let's do an interesting experiment here. We've talked about diffusion, a... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And in general, and this is not always the case, if you want to be as general as possible, the solute is whatever you have less of, the solvent is whatever you have more of. And the most common solvent tends to be water. But it doesn't have to be water. It could be some type of alcohol, it could be mercury, it could be... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
It could be some type of alcohol, it could be mercury, it could be a whole set of molecules, but water in most biological or chemical systems tends to be the most typical solvent. It's what other things are dissolved into. But what happens if we have a tunnel where the solute is too big to travel, but water is small en... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So let's think about that situation. In order to think about it, I'm going to do something interesting. Let's say we have a container here. Let's say we have, actually I won't even draw a container. Let's just say we have an outside environment that has a bunch of water. This is the outside environment. And then you ha... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Let's say we have, actually I won't even draw a container. Let's just say we have an outside environment that has a bunch of water. This is the outside environment. And then you have some type of membrane. Water can go in and out of this membrane. So it's semi-permeable. Well, it's permeable to water, but the solute ca... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And then you have some type of membrane. Water can go in and out of this membrane. So it's semi-permeable. Well, it's permeable to water, but the solute cannot go through the membrane. So let's say that the solute is sugar. So we have water on the outside and also inside the membrane. So these are little small water mo... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Well, it's permeable to water, but the solute cannot go through the membrane. So let's say that the solute is sugar. So we have water on the outside and also inside the membrane. So these are little small water molecules. This is a membrane right here. And let's say that we have some sugar molecules. I'm just picking o... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So these are little small water molecules. This is a membrane right here. And let's say that we have some sugar molecules. I'm just picking on sugar. It could have been anything. So we have some sugar molecules here that are just a little bit bigger. Or they could be a lot bigger, actually. | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
I'm just picking on sugar. It could have been anything. So we have some sugar molecules here that are just a little bit bigger. Or they could be a lot bigger, actually. They're a lot bigger than water molecules. So you have a bunch of, and I only draw four, but you have a gazillion of them. But you have that much more ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Or they could be a lot bigger, actually. They're a lot bigger than water molecules. So you have a bunch of, and I only draw four, but you have a gazillion of them. But you have that much more water molecules. I'm just trying to show you have more water molecules than sugar molecules. And this membrane is semi-permeable... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But you have that much more water molecules. I'm just trying to show you have more water molecules than sugar molecules. And this membrane is semi-permeable. Permeable means that it allows things to pass. Semi-permeable means it's not completely permeable. So semi-permeable in this context, I'm saying I allow water to ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Permeable means that it allows things to pass. Semi-permeable means it's not completely permeable. So semi-permeable in this context, I'm saying I allow water to pass through the membrane. So water can pass. But sugar cannot. Sugar is too large. And the reason why in this case is because the sugar molecule is too big. | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So water can pass. But sugar cannot. Sugar is too large. And the reason why in this case is because the sugar molecule is too big. So if we were to zoom in on the actual membrane itself, maybe the membrane looks like this. I'm going to zoom in on this membrane. So it has little holes in the membrane, just like that. | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And the reason why in this case is because the sugar molecule is too big. So if we were to zoom in on the actual membrane itself, maybe the membrane looks like this. I'm going to zoom in on this membrane. So it has little holes in the membrane, just like that. And maybe the water molecules are about that size, so they ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So it has little holes in the membrane, just like that. And maybe the water molecules are about that size, so they can go through those holes. So the water molecules can go back and forth through the holes. But the sugar molecules are about that big, so they cannot go through that hole. They're too big for this opening... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But the sugar molecules are about that big, so they cannot go through that hole. They're too big for this opening right here to go back and forth between them. Now, what do you think is going to happen in this situation? So first of all, let's use our terminology. Remember, sugar is our solute. Water is our solvent. Se... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So first of all, let's use our terminology. Remember, sugar is our solute. Water is our solvent. Semi-permeable membrane. Which side of the membrane has a higher or lower concentration of solute? Well, the inside does. The inside is hypertonic. | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Semi-permeable membrane. Which side of the membrane has a higher or lower concentration of solute? Well, the inside does. The inside is hypertonic. The outside has a lower concentration. So it's hypotonic out here. Lower concentration of solute. | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
The inside is hypertonic. The outside has a lower concentration. So it's hypotonic out here. Lower concentration of solute. Now, if these openings were big enough, based on what we just talked about, these guys are bouncing around. Water is traveling in either direction. And equal probability, or actually I'm going to ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
Lower concentration of solute. Now, if these openings were big enough, based on what we just talked about, these guys are bouncing around. Water is traveling in either direction. And equal probability, or actually I'm going to talk about that in a second. If everything was wide open, it would be equal probability. But ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And equal probability, or actually I'm going to talk about that in a second. If everything was wide open, it would be equal probability. But if it was wide open, these guys eventually would bounce their ways over to this side, and you'd probably end up with equal concentrations eventually. And so you would have your tr... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
And so you would have your traditional diffusion, where high concentration of solute to low concentration of solute. But in this case, these guys, they can't fit through the hole. Only water can go back and forth. If these guys were not here, water would have an equal likelihood of going in this direction as they would... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
If these guys were not here, water would have an equal likelihood of going in this direction as they would be going in that direction. A completely equal likelihood. But because these guys are on the right-hand side of, or in this case, on the inside of our membrane, this is our inside of our membrane zoomed up, it's l... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
It's that slightly less likely for water to be in the approach position for the holes. So it's actually more probable that water could enter than water exit. And I want to make that very clear. If these sugar molecules were not here, obviously it's equally likely for water to go in either direction. Now that these suga... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
If these sugar molecules were not here, obviously it's equally likely for water to go in either direction. Now that these sugar molecules are there, these sugar molecules might be on the right-hand side. They might be blocking, I guess the best way to think about it is blocking the approach to the hole. They'll never b... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
They'll never be able to go through the hole themselves, and they might not even be blocking the hole. But they're going in some random direction. So if a water molecule was approaching, it's all probabilistic and we're dealing with gazillions of molecules. It's that much more likely to be blocked to get outside. But t... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
It's that much more likely to be blocked to get outside. But the water molecules from the outside, there's nothing blocking them to get in. So you're going to have a flow of water inside. So in this situation, with a semipermeable membrane, you're going to have water, you're going to have a net inward flow of water. An... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So in this situation, with a semipermeable membrane, you're going to have water, you're going to have a net inward flow of water. And so this is kind of interesting. We have the solvent flowing from a hypotonic situation to a hypertonic solution. But it's only hypotonic in the solute. That's when you talk about the sol... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But it's only hypotonic in the solute. That's when you talk about the solute. And it's only hypertonic when you talk about the solute. But water, if you flip it the other way, if you view sugar as the solvent, then you could say we're going from a high concentration of water to a low concentration of water. I don't wan... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But water, if you flip it the other way, if you view sugar as the solvent, then you could say we're going from a high concentration of water to a low concentration of water. I don't want to confuse you too much. This is what tends to confuse people. But just think about what's going to happen. No matter what, in what s... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But just think about what's going to happen. No matter what, in what situation, the solution is going to do what it can to try to equilibrate the concentration, to make the concentrations on both sides as close as possible. And it's not just some magic. It's not like the solution knows. It's all based on probabilities ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
It's not like the solution knows. It's all based on probabilities and these things bumping around. But in this situation, water is more likely to flow into the container. So it's actually going to go from the hypotonic side, when we talk about low concentration of solute, to the side that has high concentrations of sol... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
So it's actually going to go from the hypotonic side, when we talk about low concentration of solute, to the side that has high concentrations of solute, of sugar. And actually, if this thing is stretchable, more water will keep flowing in. And this membrane will stretch out. But we won't go into too much detail here. ... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But we won't go into too much detail here. But this idea of water, of the solvent, if in this case, water is the solvent, of water as a solvent diffusing through a semipermeable membrane, this is called osmosis. You've probably heard learning by osmosis. You know, if you put a book against your head, maybe it'll just s... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
You know, if you put a book against your head, maybe it'll just seep into your brain. Same idea. That's where the word comes from. This idea of water seeping through membranes to try to make concentrations more equal. So if you say, well, you see I have high concentration here, low concentration here. If there was no m... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
This idea of water seeping through membranes to try to make concentrations more equal. So if you say, well, you see I have high concentration here, low concentration here. If there was no membrane here, these big molecules would exit. But because there's this semipermeable membrane here, they can't. So the system, just... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
But because there's this semipermeable membrane here, they can't. So the system, just probabilistically, no magic here, more water will enter to try to equilibrate the concentration. And eventually, if maybe there's a few molecules out here, not as high concentration here, eventually if everything was allowed to happen... | Diffusion and osmosis Membranes and transport Biology Khan Academy.mp3 |
We humans have known for thousands of years, just looking at our environment around us, that there are different substances. And these different substances tend to have different properties. And not only do they have different properties, one might reflect light in a certain way or not reflect light, or be a certain co... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
But we also start to observe how they react with each other in certain circumstances. And here's pictures of some of these substances. This right here is carbon. And this is in its graphite form. This right here is lead. This right here is gold. And all of the ones that I've shown pictures of here, and I got them all f... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And this is in its graphite form. This right here is lead. This right here is gold. And all of the ones that I've shown pictures of here, and I got them all from this website right over there, all of these are in their solid form. But we also know that it looks like there's certain types of air and certain types of air... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And all of the ones that I've shown pictures of here, and I got them all from this website right over there, all of these are in their solid form. But we also know that it looks like there's certain types of air and certain types of air particles. And depending on what type of air particles you're looking at, whether i... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
Or there are other things that can be liquid. Or even if you raise the temperature high enough on these things, if you raise the temperature high enough on gold or lead, you could get a liquid. Or if you burn this carbon, you can get it to a gaseous state, you can release it into the atmosphere, you can break its struc... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
So these are things that humanity has observed for thousands of years. But it leads to a natural question that used to be a philosophical question, but now we can answer it a little bit better. And that question is, if you keep breaking down this carbon into smaller and smaller chunks, is there some smallest chunk, som... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And if you were to somehow break that down even further, somehow you would lose the properties of the carbon. And the answer is, there is. And so just to get our terminology, we call these different substances, these pure substances that have these specific properties at certain temperatures and react in certain ways, ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
Carbon is an element. Lead is an element. Gold is an element. You might say that water is an element. And in history, people have referred to water as an element. But now we know that water is made up of more basic elements. It's made of oxygen and of hydrogen. | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
You might say that water is an element. And in history, people have referred to water as an element. But now we know that water is made up of more basic elements. It's made of oxygen and of hydrogen. And all of our elements are listed here in the periodic table of elements. C stands for carbon. I'm just going through t... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
It's made of oxygen and of hydrogen. And all of our elements are listed here in the periodic table of elements. C stands for carbon. I'm just going through the ones that are very relevant to humanity, but over time you'll probably familiarize yourself with all of these. This is oxygen. This is nitrogen. This is silicon... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
I'm just going through the ones that are very relevant to humanity, but over time you'll probably familiarize yourself with all of these. This is oxygen. This is nitrogen. This is silicon. This is, Au is gold. This is lead. And that most basic unit of any of these elements is the atom. | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
This is silicon. This is, Au is gold. This is lead. And that most basic unit of any of these elements is the atom. So if you were to keep digging in and keep taking smaller and smaller chunks of this, eventually you would get to a carbon atom. Do the same thing over here. Eventually you would get to a gold atom. | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And that most basic unit of any of these elements is the atom. So if you were to keep digging in and keep taking smaller and smaller chunks of this, eventually you would get to a carbon atom. Do the same thing over here. Eventually you would get to a gold atom. You did the same thing over here. Eventually you'd get som... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
Eventually you would get to a gold atom. You did the same thing over here. Eventually you'd get some, this little small, for lack of a better word, particle that you would call a lead atom. And you wouldn't be able to break that down anymore and still call that lead, for it to still have the properties of lead. And jus... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And you wouldn't be able to break that down anymore and still call that lead, for it to still have the properties of lead. And just to give you an idea, and this is really something that I have trouble imagining, is that atoms are unbelievably small, really unimaginably small. So for example, carbon. My hair is also ma... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
My hair is also made out of carbon. In fact, most of me is made out of carbon. In fact, most of all living things are made out of carbon. And so if you took my hair, and so my hair is carbon, my hair is mostly carbon. So if you took my hair right over here, and my hair isn't yellow, but it contrasts nicely with the bla... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And so if you took my hair, and so my hair is carbon, my hair is mostly carbon. So if you took my hair right over here, and my hair isn't yellow, but it contrasts nicely with the black, my hair is black, but if I did that you wouldn't be able to see it on the screen. But if you took my hair here, and I were to ask you ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
What is the diameter? So if you took a cross section of my hair, not the length, the width of my hair, and said how many carbon atoms wide is that, and you might guess, oh, Sal already told me they're very small, so maybe there's 1,000 carbon atoms there, or 10,000 or 100,000. I would say no. There are 1,000,000 carbon... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
There are 1,000,000 carbon atoms, or you could string 1,000,000 carbon atoms across the width of the average human hair. And that's obviously an approximation. It's not exactly 1,000,000, but that gives you a sense of how small an atom is. You know, pluck a hair out of your head, and just imagine putting a million thin... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
You know, pluck a hair out of your head, and just imagine putting a million things next to each other across the hair. Not the length of the hair, the width of the hair. It's even hard to see the width of a hair, and there would be a million carbon atoms just going along it. Now, it would be pretty cool in and of itsel... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
Now, it would be pretty cool in and of itself that we do know that there is this most basic building block of carbon, this most basic building block of any element. But what's even neater is that those basic building blocks are related to each other. A carbon atom is made up of even more fundamental particles. A gold a... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
A gold atom is made up of even more fundamental particles. And they're actually defined by the arrangement of those fundamental particles. And if you were to change the number of fundamental particles you have, you could change the properties of the element, how it would react, or you could even change the element itse... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And just to understand it a little bit better, let's talk about those fundamental elements. So you have the proton. And the proton is actually the defining the number of protons in the nucleus of an atom. And I'll talk about the nucleus in a second. That is what defines the element. So this is what defines an element. ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And I'll talk about the nucleus in a second. That is what defines the element. So this is what defines an element. When you look at the periodic table right here, they're actually written in order of atomic number. And the atomic number is literally just the number of protons in the element. So by definition, hydrogen ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
When you look at the periodic table right here, they're actually written in order of atomic number. And the atomic number is literally just the number of protons in the element. So by definition, hydrogen has one proton. Helium has two protons. Carbon has six protons. You cannot have carbon with seven protons. If you d... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
Helium has two protons. Carbon has six protons. You cannot have carbon with seven protons. If you did, it would be nitrogen. It would not be carbon anymore. Oxygen has eight protons. If somehow you were to add another proton to there, it wouldn't be oxygen anymore. | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
If you did, it would be nitrogen. It would not be carbon anymore. Oxygen has eight protons. If somehow you were to add another proton to there, it wouldn't be oxygen anymore. It would be fluorine. So it defines the element. And the atomic number, the number of protons, and remember, that's the number that's written rig... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
If somehow you were to add another proton to there, it wouldn't be oxygen anymore. It would be fluorine. So it defines the element. And the atomic number, the number of protons, and remember, that's the number that's written right at the top here for each of these elements in the periodic table, the number of protons i... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And the atomic number, the number of protons, and remember, that's the number that's written right at the top here for each of these elements in the periodic table, the number of protons is equal to the atomic number. And they put that number up here because that is the defining characteristic of an element. The other ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And the model you can start to build in your head, and this model as we go through chemistry, it'll get a little bit more abstract and really hard to conceptualize. But one way to think about it is you have the protons and the neutrons that are at the center of the atom. They're the nucleus of the atom. So for example,... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
So for example, carbon we know has six protons. So one, two, three, four, five, six. Carbon-12, which is a version of carbon, will also have six neutrons. You can have versions of carbon that have a different number of neutrons. So the neutrons can change, the electrons can change, you can still have the same element. ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
You can have versions of carbon that have a different number of neutrons. So the neutrons can change, the electrons can change, you can still have the same element. The protons can't change. If you change the protons, you've got a different element. So let me draw a carbon-12 nucleus. So one, two, three, four, five, si... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
If you change the protons, you've got a different element. So let me draw a carbon-12 nucleus. So one, two, three, four, five, six. So this right here is the nucleus of carbon-12. And sometimes it'll be written like this, and sometimes they'll actually write the number of protons as well. And the reason why we write it... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
So this right here is the nucleus of carbon-12. And sometimes it'll be written like this, and sometimes they'll actually write the number of protons as well. And the reason why we write it carbon-12, I counted out six neutrons, is that you could view this as the total number of one way to view it, and we'll get a littl... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And this carbon, by definition, has an atomic number of six, but we can rewrite it here just so that we can remind ourselves. So at the center of a carbon atom, we have this nucleus. And carbon-12 will have six protons and six neutrons. Another version of carbon, carbon-14, will still have six protons, but then it woul... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
Another version of carbon, carbon-14, will still have six protons, but then it would have eight neutrons. So the number of neutrons can change. But this is carbon-12 right over here. And if carbon-12 is neutral, and I'll give a little nuance on this word in a second as well, if it is neutral, it'll also have six electr... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And if carbon-12 is neutral, and I'll give a little nuance on this word in a second as well, if it is neutral, it'll also have six electrons. So let me draw those six electrons. One, two, three, four, five, six. And one way, and this is maybe the first order way of thinking about the relationship between the electrons ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And one way, and this is maybe the first order way of thinking about the relationship between the electrons and the nucleus, is that you can imagine the electrons are kind of moving around, buzzing around this nucleus. One model is you could kind of think of them as orbiting around the nucleus, but that's not quite rig... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
But that's a good starting point. Another way is they're kind of jumping around the nucleus, or they're buzzing around the nucleus. And that's just because reality just gets very strange at this level, and we'll actually have to go into quantum physics to really understand what the electron is doing. But a first mental... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
But a first mental model in your head is that the center of this atom, of this carbon-12 atom, you have this nucleus right over there. And these electrons are jumping around this nucleus. And the reason why these electrons don't just go off away from this nucleus, why they're kind of bound to this nucleus and they form... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And it's one of these properties of these fundamental particles. When you start thinking about, well, what is a charge fundamentally, other than a label, and it starts to get kind of deep. But the one thing that we know when we talk about electromagnetic force is that unlike charges attract each other. So the best way ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
So the best way to think about it is protons and electrons, because they have different charges, they attract each other. Neutrons are neutral. So they're really just sitting here inside of the nucleus. And they do affect the properties on some level for some atoms of certain elements. But the reason why we have the el... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And they do affect the properties on some level for some atoms of certain elements. But the reason why we have the electrons not just flying off on their own is because they are attracted. They are attracted towards the nucleus. And they also have an unbelievably high velocity. It's actually hard for, and we start touc... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And they also have an unbelievably high velocity. It's actually hard for, and we start touching once again on a very strange part of physics, once we start talking about what an electron actually is doing. But it has enough, I guess you could say it's jumping around enough that it doesn't want to just fall into the nuc... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And so I mentioned carbon-12 right over here, defined by the number of protons. Oxygen would be defined by having eight protons. But once again, electrons can interact with other electrons, or they can be taken away by other atoms. And that actually forms a lot of our understanding of chemistry. It's based on how many ... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
And that actually forms a lot of our understanding of chemistry. It's based on how many electrons an atom has, or a certain element has, and how those electrons are configured, and how the electrons of other elements are configured, or maybe other atoms of that same element. We can start to predict how an atom of one e... | Elements and atoms Atoms, compounds, and ions Chemistry Khan Academy.mp3 |
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