An atom splits when it is struck by a neutron. The nucleus of the atom then breaks into two roughly equal parts and, at the same time, shoots out several high-speed neutrons.
Atoms are so small that they cannot be seen under the most powerful microscope. They are the building bricks of which each element is composed. The Greek word “atom” means “cannot be cut”. But we know how that atoms can be cut, or split. Each one contains minute particle carrying two sorts of electricity: first the electrons which are negatively charged; and secondly, the central core or nucleus which is made up of protons (positively charged) and neutrons (no charge).
In the 19th century it was discovered that all elements with atomic weights greater than 83 are radioactive and that the nucleus could be divided into several parts. Albert Einstein (1879-1955) calculated in 1905 that splitting an atom would destroy mass and release heat. By thus converting matter into heat energy, vast amounts of heat would be obtained by destroying only a very small amount of matter.
Between 1934 and 1938 the Italian Enrico Fermi and the German Otto Hahn discovered that atoms of uranium (atomic weight 92) split when struck by a neutron. In 1939 Fredric Joliot-curie found that this splitting, or fission, released two or three more neutrons which in turn produced fission in more uranium nuclei, and so on. It is this chain reaction that makes possible not only the benefits of nuclear power but also the horrors of nuclear warfare.
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