Define nuclear fission giving one example.

Explanation

### Step-by-Step Text Solution:

1. **Definition of Nuclear Fission**:
- Nuclear fission is a nuclear reaction in which a heavy and unstable atomic nucleus splits into two smaller nuclei, along with the release of a significant amount of energy. This process typically occurs when the nucleus absorbs a neutron, becoming unstable and subsequently splitting.

2. **Process of Nuclear Fission**:
- In a typical fission reaction, the heavy nucleus (like Uranium-235) absorbs a neutron. This absorption makes the nucleus unstable, leading it to split into two lighter nuclei. During this splitting process, additional neutrons are released, and a large amount of energy is emitted.

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