Do not tell anyone this.
There are two sorts of atomic explosions, those caused by nuclear fission and those caused by nuclear fusion. Each involves altering the amount of matter contained in atoms to reduce their mass and create the energy that manifests itself as a huge explosion. The former splits atoms to create two new ones from each, the total mass of which will be less than the original atom; fusion will join two atoms together to result in one single new atom that will be less than the original two. It’s The difference in mass between what you started with and what you end up with that is converted into the energy that creates the explosion.
The chain reaction that occurs to give a nuclear bomb its power happens in a fission explosion when the atoms of an unstable “fissile” material — uranium, which consists of protons, neutrons, and electrons — are bombarded with extra neutrons, and split to release free neutrons of their own, which in turn cannon into other atoms in the uranium. The energy released as this happens is enormous.
A nuclear fusion explosion creates an even greater energy surge than fission, but for a long time was harder to achieve. It uses hydrogen not uranium (this is why some atomic bombs are referred to as hydrogen bombs) and fuses together two of the different atoms that make up the gas to create one single atom. Because these atoms, deuterium and tritium, naturally repel each other, they have to be heated to a temperature of over a million degrees centigrade before they fuse. But once that temperature is reached the fusion takes place in all atoms at once, creating an explosion of energy. In power stations, lasers are fired at pellets of extracted deuterium and tritium, but in a fusion bomb, a small fission device will be used as the trigger to create temperature for fusion to occur.
