Atoms are incredibly small, but they are also incredibly dense. The nucleus of an atom is made up of protons and neutrons, which are held together by the strong force. When an atom is split, the nucleus is released and the protons and neutrons are free to interact with each other. This interaction releases a tremendous amount of energy, which is why splitting atoms can cause such a large explosion.

The amount of energy released when an atom is split is proportional to the mass of the atom. For example, splitting a single atom of uranium-235 releases about 200 million electronvolts (MeV) of energy. This may not seem like a lot, but it is a lot of energy for such a small amount of matter.

To put this into perspective, a single gram of uranium-235 contains about 20 trillion atoms. If all of these atoms were to be split, the energy released would be equivalent to about 1 ton of TNT. This is why nuclear weapons are so powerful.

In addition to the energy released, splitting atoms also releases neutrons. These neutrons can then go on to split other atoms, which can create a chain reaction. This chain reaction is what causes a nuclear explosion to be so destructive.

It is important to note that not all atoms can be split. Only certain atoms, such as uranium-235 and plutonium-239, are fissile. These atoms have a nucleus that is unstable and can be split by a neutron. Other atoms, such as hydrogen and helium, are not fissile and cannot be split by a neutron.