In the 1930s, scientists found out that if a neutron is fired into certain uranium atoms, they could split into two and emit a certain number of neutrons, releasing a huge amount of energy along the way. This is called fission, from the Latin word for ’split’.
Uranium, with 92 protons, has the highest atomic number of all naturally occurring elements on Earth. Uranium-235 is easier to split (fission) than other isotopes because its nucleus is relatively unstable, and readily absorbs a neutron, causing it to break apart into two lighter atoms. However, only 0.7 per cent of uranium found on earth is this type of uranium, described as fissile.
Read more about uranium here.
