Two lithium nuclei in a lithium vapour at room temperature do not combine to form a carbon nucleus because

Options

A. Carbon nucleus is an unstable particle
B. It is not energetically favorable
C. Nuclei do not come very close due to close due to Coulombic repulsion
D. Lithium nucleus is more tightly bound than a carbon nucleus

Answer

To solve the question of why two lithium nuclei in a lithium vapor at room temperature do not combine to form a carbon nucleus, we can analyze the situation step by step.

### Step-by-Step Solution:

1. **Understanding Nuclei Composition**:
- Lithium (Li) has an atomic number of 3, meaning it has 3 protons in its nucleus. When two lithium nuclei combine, they would need to overcome certain forces to form a heavier nucleus, such as carbon (C), which has an atomic number of 6.

**Hint**: Remember that the atomic number indicates the number of protons in the nucleus, which influences nuclear stability.

2. **Coulomb's Law and Repulsion**:
- Both lithium nuclei are positively charged due to the presence of protons. According to Coulomb's law, like charges repel each other. Therefore, when two lithium nuclei approach each other, they experience a repulsive force due to their positive charges.

**Hint**: Consider how charges interact; like charges repel while opposite charges attract.

3. **Energy Considerations**:
- For nuclear fusion (the process of combining two nuclei) to occur, it must be energetically favorable. This means that the reaction should release energy. The binding energy of the resulting nucleus (carbon) must be greater than the binding energy of the initial lithium nuclei for the reaction to be favorable.

**Hint**: Think about binding energy; a higher binding energy in the product means a more stable nucleus.

4. **Temperature Factor**:
- At room temperature, the kinetic energy of the lithium nuclei is not sufficient to overcome the Coulomb barrier (the energy barrier due to repulsion). High temperatures, such as those found in stars, provide enough energy for nuclei to overcome this barrier and fuse.

**Hint**: Recall that temperature relates to kinetic energy; higher temperatures can help overcome energy barriers.

5. **Conclusion**:
- The primary reason two lithium nuclei do not combine at room temperature is due to the Coulomb repulsion between the positively charged protons in the nuclei. This repulsion prevents them from coming close enough to undergo fusion.

**Hint**: Focus on the forces acting between the nuclei and the energy conditions required for fusion.

### Final Answer:
Two lithium nuclei in a lithium vapor at room temperature do not combine to form a carbon nucleus primarily due to Coulombic repulsion between their positively charged protons, which prevents them from coming close enough to fuse.