eli5: What exactly is silicone and why is it so essential to making electronics ?
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First, we need to distinguish between the element *silicon* and *silicone* which is a polymer made from silicon and oxygen. Silicon is what electronics need.
Silicon is a *semiconductor*. That means it kind of wants to conduct electricity, but it also kind of doesn’t. Silicon is like carbon, in that it has 4 electrons in the outermost shell. Atoms are most stable if there are 8 electrons in the outermost shell. Elements with more than 4 electrons tend to try to grab more electrons and fill up that shell. Elements with less than 4 tend to try to get rid of electrons so the “outermost” shell is empty and the next lowest full shell becomes the outermost shell. Different atoms will share electrons between each other so that they can all have a full (or empty) outer shell. Since silicon has 4, it can give up electrons *or* gain electrons. Multiple silicon atoms together will share with each other [like this](https://www.pveducation.org/sites/default/files/PVCDROM/PN-Junction/Images/BOND-SI.GIF) so that *together* each atom has 8 electrons.
It can also be “doped” with other elements to change how conductive it is. Let’s look at a really simple example like a *diode*. A diode is kind of like a check-valve or gate for electricity that only allows it to flow in one direction through the diode. A diode is made of two sides with silicon that are doped with different elements that make them *positive* or p-type and *negative* or n-type. For the positive side, boron is added into the silicon. Boron has only 3 electrons in the outer shell. Like the silicon around it, the boron atom wants to share the electrons so that together all of them have 8, but since boron only has 3 to share with the silicon’s 4, that means they’re missing one. This creates a positive “hole” that an electron can fall into. That electron has to come from somewhere, which is going to be one of the silicon atoms next to it. Now that silicon atom is missing an electron and will want to grab one from another silicon atom. This allows the “hole” to move around inside the silicon and makes the piece slightly positively charged, or p-type.
If phosphorus is added instead, the silicon becomes slightly negatively charged. As before, the phosphorus shares its electrons with the silicon to form 8, but since phosphorus has 5 instead of 4, there’s an extra electron that needs to go somewhere. That electron gets in the way of additional electrons that may want to flow through the silicon. That makes the doped silicon slightly negatively charged, or n-type.
A diode is made by putting n-type and p-type pieces of silicon together, [like this](https://i.pinimg.com/736x/e5/0b/17/e50b172ea3af5cb18d9494613993a5cb.jpg). Where the two sides are touching, the extra electrons from the n-type flow over and fill up the holes in the p-type, creating the neutral region between them. If a voltage is applied that wants to make electrons flow from the n side to the p side, current will flow. The positive side of the voltage “sucks” electrons out of the p-type silicon, creating holes that electrons can flow into from the n-type side. The negative side of the voltage pushes electrons against the n-type silicon, creating a pressure to keep pushing electrons from the n side into the holes forming in the p side.
If the voltage is reversed, though, current can’t flow. The negative side of the voltage fills up all the holes in the p-type silicon, but the extra electrons in the n-type silicon get in the way and stop more from moving over. The positive side of the voltage will suck away some of the extra electrons from that side, but that doesn’t make positive holes, it just makes the silicon neutral. There’s still no room for additional electrons to come from the now-full p-side. So, no current will flow (until you apply so much voltage that it overloads the diode and breaks down the silicon).
More advanced parts can be made by doping the silicon and arranging [it the right way](https://www.electronics-tutorials.ws/wp-content/uploads/2013/09/tran5.gif). You can use voltage to control whether or not there are holes or electrons in the silicon, which would either allow current to flow or block current from flowing. This lets you use one signal to control another signal.
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