Which of the following is most unstable

Options

A. `alpha`-particle
B. Neutrons
C. `beta`-particle
D. `beta^+`-particle

Answer

To determine which of the given particles is the most unstable, we can analyze the stability of each particle mentioned in the question.

### Step-by-Step Solution:

1. **Identify the Particles**: The question mentions several particles, including free neutrons, alpha particles, beta particles, and positrons (E+).

2. **Analyze the Free Neutron**:
- A free neutron is known to be unstable. It undergoes beta decay, where it disintegrates into a proton, an electron (beta particle), and an anti-neutrino.
- The half-life of a free neutron is approximately 15 minutes. This means that it will decay into other particles over time, indicating its instability.

3. **Analyze the Alpha Particle**:
- An alpha particle is essentially a helium nucleus (two protons and two neutrons). It is generally considered stable when it is part of a larger nucleus.
- Alpha particles can be emitted from unstable heavy nuclei, but in isolation, they are stable.

4. **Analyze the Beta Particle**:
- A beta particle is an electron emitted during beta decay. Electrons are stable particles and do not decay further under normal conditions.

5. **Analyze the Positron (E+)**:
- A positron is the antiparticle of the electron. While it can annihilate with an electron to produce gamma rays, it is also considered stable in isolation.

6. **Conclusion**:
- Among the particles analyzed, the free neutron is the most unstable due to its relatively short half-life and its tendency to decay into other particles.
- Therefore, the correct answer is that the free neutron is the most unstable particle.

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

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