And if splitting atom releases energy, why haven’t these energy break from their atom themselves? Isn’t that means the force that bind the atoms are bigger than the energy released?
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Iron is the magic element. Everything below Iron releases more energy than it takes to fuse the atoms. Everything above Iron releases more energy than it takes to split the atom.
We don’t see random nuclear explosions because a nuclear explosion is an incredibly fast *chain* reaction. Splitting an atom releases (amongst other things) fast moving neutrons. If any of those neutrons hit an atom they will impart their energy to it and if it’s sufficiently unstable then it, too, will fall apart in a burst of energy and neutrons. And if any of those neutrons hits an atom they will impart their energy to it and… well, you get the picture.
The problem is neutrons are smaller than an atom and have no charge so they are not attracted by atoms. Solid matter is mostly empty space between the atoms, so the neutrons can go a fair distance before they hit anything.
So make an nuclear bomb, the first thing we needed was a *lot* of “sufficiently unstable” material. Not all uranium (or whatever the bomb you’re talking about happens to be made of) is created equal, there are different isotopes — that is, versions of the element which all have the same number of protons but have different numbers of neutrons. Some isotopes are more stable than others.
If we used the slightly more stable version of uranium the bomb wouldn’t work. We couldn’t get the chain reaction. So we had to process a *lot* of uranium ore to extract the small amounts of extremely unstable uranium present in it.
But we’re done yet. Now we need to get a “critical mass” of uranium at the same place all at once. If there’s not enough of that highly unstable uranium smooshed together as densely as possible enough of the neutrons would fly through the uranium without hitting enough other uranium to create a sustained chain reaction.
We solved this problem by, basically, creating two masses that were *almost* a critical mass and using precisely timed explosions with conventional explosives to drive those two masses together into one where there’s enough stuff in a small enough space to trigger that chain reaction.
So why haven’t they broken themselves? They do. All the time. Radioactive material is slightly warmer than ambient from the energy released. And, well, that energy is also the radiation in “radioactive.” It’s just really, really slow, at least when compared to an explosion because they’re spontaneously falling apart rather than being driven apart in a chain reaction. When looking at radioactive elements a key piece of information presented is “half-life.” This is the amount of time it takes for roughly half the material to fall apart. A half-life of 12 years means that if you have a pound of it then in 12 years you will have half a pound of it and half a pound of whatever it decays into.
It’s like the difference between lighting a candle and lighting a firecracker. The candle will output more total energy, but the firecracker will be much more abrupt about the energy it’s releasing.
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