The statement that "atoms cannot be destroyed" is generally true. According to the law of conservation of mass and energy, atoms are not created or destroyed in ordinary chemical reactions or physical processes. However, it is possible to split an atom through a process called nuclear fission.
Nuclear fission involves breaking apart the nucleus of an atom, typically a heavy and unstable nucleus such as uranium-235 or plutonium-239. When a heavy nucleus absorbs a neutron, it becomes highly unstable and can split into two or more smaller nuclei. This process releases a significant amount of energy and additional neutrons, which can then induce a chain reaction, leading to the splitting of more atoms.
It's important to note that during nuclear fission, the total number of protons and neutrons (the atomic mass) is conserved. However, the energy released during this process is immense and is a result of the conversion of mass into energy, as described by Einstein's famous equation, E=mc². A small amount of mass is converted into a large amount of energy according to this equation.
So, while the atoms themselves are not destroyed in nuclear fission, their nuclei are split, releasing a tremendous amount of energy. This process is harnessed in nuclear power plants and nuclear weapons.