Which best describes nuclear fission?

Question

1. A nucleus spontaneously splits and absorbs energy.
2. Two nuclei spontaneously combine and absorb energy.
3. A nucleus collides with a neutron and splits, releasing energy.
4. Nuclei combine to form a heavier nucleus, releasing energy.

Answer 1

The statement that best describes nuclear fission is:

3. A nucleus collides with a neutron and splits, releasing energy.

In nuclear fission, a heavy nucleus (such as uranium-235 or plutonium-239) absorbs a neutron, becomes unstable, and then splits into two or more smaller nuclei, along with the release of energy and additional neutrons.