Two examples of nuclear change are fission and fusion. Nuclear change refers to a change in the nucleus of an atom as opposed to its electrons, as in a chemical change.
There are three types of change: physical, chemical, or nuclear. Physical change can be undone by physical means, as when a water molecule changes to ice and back to water again. A chemical change involves the bonds of the electrons, as in when two elements react with each other. A nuclear change involves a change in the atomic nucleus. In nuclear change an element can become an entirely different element; atoms change in weight, number, and type. In a kind of nuclear change called fission, the nucleus splits. In a kind called fusion, neutrons and protons combine to create heavier atoms. A nuclear change involves 1,000,000 times more energy than a chemical change.