A form of nuclear (atomic) reaction produced by splitting the nucleus of a heavy atom into two or more lighter nuclei. The term "splitting atoms" stems from the process of nuclear fission, but it should be noted that splitting the nucleus is what produces the energy. Changing the number of electrons has relatively little effect in comparison.

Fission is the simplest way of generating nuclear energy, and all current nuclear energy facilities use fission reactors. More efficient fusion reactors are still not commercially viable.

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