 The most exciting and important parts of electronic components are made from crystals, which are made with semiconductors. A silicon atom is going to have four valence electrons, so we take a look at this guy, one, two, three, four. However, it wants to have eight. When we have a valence shell, the last shell, they want to have eight. That's the maximum number of electrons you will have in a valence. This is a problem, so what it ends up doing is this guy right here, this silicon atom, he's going to hook up with a bunch of his buddies and they're going to share their valence electrons. They're going to share them around so they each have eight valence electrons. This creates what we call a crystal lattice structure or a crystal. Let's take a look at what that looks like. Here we've got a bunch of silicon atoms milling about. They're chilling. They meet up. If we see here, they've got one, two, three, four, five, six. Then this guy, if he had one up here, seven, eight, they're all sharing them. Here's a great example. One, two, three, four, five, six, seven, eight. He's sharing his with him and him and him and him and they're all sharing them together and they're creating this crystal lattice. On its own, this crystal lattice isn't very useful, but if we add something to the recipe when this guy is starting to grow, if we add some sort of what's called an impurity, then we can make them extremely useful. We can give them a little bit of a conductive property or we can give them a little bit of an insulator property. We usually use boron or phosphorus. We add that to the recipe and it makes the crystal extremely useful. Now that is called doping. Unlike the kind of doping where you guys would probably take the van down to the river and you know what I'm saying. This is by injecting an impurity into this crystal lattice, we can give it different properties. Let's take a look at it. What we got here is your basic P-type semiconductor crystal. Before we had nothing but all this and all this and all this, we're all silicon atoms, but you notice now here, we've added this guy in. It's a boron atom, so we've injected this impurity into this crystal lattice structure. It, if you notice, is missing an electron. So there's a problem right there is it doesn't have an electron, so what it leaves is an extra hole. We call this a P-type because it has a deficiency of electrons or an excess of holes. It's like, and the P-type comes from when it's like that, it is a positive charge. It's like the old joke where an atom walks into a bar and it says to his buddy, hey buddy, I think I'm missing an electron. And his friend says, are you sure? And he says, I'm positive, get it? So he's missing an electron and it is a positive charge. So he has an extra hole here. Well, these electrons that are milling about and these guys will kind of all be hopping around, bumping each other. Now they've got a place to go. So this guy might bump this guy, which will move him to that hole. And we get electrons flowing. And when this guy bumps, then it opens up a hole here. That guy fills it. That guy moves. And we start seeing all this random current flow as it's flowing around, bumping electrons in and out of place because it's got this extra hole. We call that P-type. This is boron here and it's called trivalent. It's a trivalent material because it has tri, which is three valence electrons. So it ends up giving us a positive charge, which means a deficiency of electrons. The next one. This guy right here we're going to call the N-type. Now instead of boron, what we've done is we've added phosphorus. And we look here, we've got this phosphor atom that we inject into it. It's an impurity and it has an extra electron. So we've got this extra one right here. And with this extra electron, it can move relatively easy through the crystal. And when this guy starts moving, he bumps and bumps and bumps. And again, we get current flowing. So we called it the N-type because it is a negative charge, which means it has a surplus of electrons. And I don't have any cheesy joke to go with that. So we've got your N-type and your P-type. P-type having extra holes and it's trivalent. N-type having extra electrons and we call it pentavalent because this guy instead of having four electrons in its valence shell like a semiconductor would, it has five. And it's sharing them with all these guys. In the next video, we're going to see what happens when we take an N-type and we put it next to a P-type. And that's where all the magic starts happening, where we end up getting a diode. We'll see you in the next one.