Not all atoms can be split to create a nuclear reaction. The process of splitting an atom is known as nuclear fission, and it typically involves certain types of atoms, specifically those that are considered fissile or capable of undergoing fission.
The most commonly used atom for nuclear fission is uranium-235 (^235U). When a uranium-235 atom absorbs a neutron, it becomes highly unstable and splits into two smaller nuclei, releasing a large amount of energy in the process. This is the basis for nuclear power plants and nuclear weapons.
Another fissile isotope is plutonium-239 (^239Pu), which can also undergo fission when bombarded with neutrons. Plutonium-239 is artificially produced from uranium-238 in nuclear reactors.
These two isotopes, uranium-235 and plutonium-239, are the primary fuel sources for nuclear fission reactions. Other isotopes, such as uranium-233 and certain isotopes of thorium, can also sustain a fission chain reaction under specific conditions.
It's important to note that not all atoms are fissile and capable of sustaining a chain reaction. Most atoms are stable or require extremely high-energy processes, such as particle accelerators, to induce nuclear reactions. Additionally, atoms that can undergo nuclear fusion, such as hydrogen isotopes, are not split but rather combined to release energy. Nuclear fusion reactions require extremely high temperatures and pressures, such as those found in the core of the Sun or in hydrogen bombs.
In summary, nuclear fission reactions generally involve specific fissile isotopes, such as uranium-235 and plutonium-239, rather than any atom.