Which of the following particles is most unstable?

Options

A. Neutron
B. Proton
C. Electron
D. `alpha` particle

Answer

To determine which of the following particles is the most unstable among neutron, proton, electron, and alpha particle, we can analyze the stability of each particle based on their properties and decay modes.

### Step-by-Step Solution:

1. **Understanding Particle Stability**:
- Stability of a particle refers to its tendency to remain unchanged over time. Unstable particles will undergo decay, transforming into other particles.

2. **Analyzing Each Particle**:
- **Neutron**: In free or isolated state, a neutron is unstable and has a half-life of about 14 minutes. It decays into a proton, an electron, and an antineutrino through beta decay.
- **Proton**: Protons are considered stable in isolation. They do not decay under normal conditions, although some theories suggest they may have an extremely long half-life (greater than 10^34 years).
- **Electron**: Electrons are stable particles and do not undergo decay. They are fundamental particles and do not have any known decay modes.
- **Alpha Particle**: An alpha particle is a helium nucleus (two protons and two neutrons). It is relatively stable but can be emitted during the decay of heavy nuclei. However, it is more stable than a free neutron.

3. **Conclusion**:
- Among the particles listed, the neutron is the most unstable when in a free state, as it decays relatively quickly compared to the others. Therefore, the answer is the neutron.

### Final Answer:
The most unstable particle among the given options is the **neutron**.

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