The phenomenon of radioactivity is associated with

Options

A. Decay of nucleus
B. Fussion of nucleus
C. Emission of electrons or protons
D. Rearragement in the in the extra nuclear electron

Answer

To solve the question "The phenomenon of radioactivity is associated with," we will analyze the options provided and determine which one correctly describes the phenomenon of radioactivity.

### Step-by-Step Solution:

1. **Understanding Radioactivity**:
- Radioactivity is a natural process where unstable atomic nuclei lose energy by emitting radiation. This process can lead to the transformation of one element into another.

2. **Analyzing the Options**:
- **Decay of Nucleus**: This refers to the process where an unstable nucleus loses energy and particles, which is a fundamental aspect of radioactivity.
- **Fusion of Nucleus**: Fusion is the process where two light nuclei combine to form a heavier nucleus, which is not related to radioactivity.
- **Emission of Electrons or Protons**: While radioactive decay can involve the emission of particles, it specifically refers to alpha, beta, and gamma radiation, not just any electrons or protons.
- **Rearrangement in the Extra Nuclear Electron**: This option refers to changes in the electron cloud surrounding the nucleus, which is not directly related to the phenomenon of radioactivity.

3. **Identifying the Correct Answer**:
- The most appropriate option that describes the phenomenon of radioactivity is **Decay of Nucleus**. This is because radioactivity is fundamentally about the decay of unstable nuclei, resulting in the emission of radiation.

### Conclusion:
The phenomenon of radioactivity is associated with the **decay of the nucleus**.

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