Statement I:Heavy nuclides tend to have more number of neutrons than protons.
Staements II: In hevay nuclei, as there is coloumbic repulsion between protons, so excess of neutrons are preferable:

Explanation

To analyze the statements provided in the question, we will break down the reasoning step by step.

### Step 1: Understanding Statement I
**Statement I:** Heavy nuclides tend to have more number of neutrons than protons.

- **Explanation:** In heavy nuclei, such as uranium-235, the number of protons (atomic number) is 92. The total number of nucleons (protons + neutrons) is 235. Therefore, the number of neutrons can be calculated as:
\[ \text{Number of neutrons} = \text{Total nucleons} - \text{Number of protons} = 235 - 92 = 143 \]
- Since 143 (neutrons) is greater than 92 (protons), this confirms that heavy nuclides do indeed have more neutrons than protons.

### Step 2: Understanding Statement II
**Statement II:** In heavy nuclei, as there is Coulombic repulsion between protons, so excess of neutrons are preferable.

- **Explanation:** Protons are positively charged particles, and like charges repel each other due to Coulomb's law. In a nucleus, as the number of protons increases, the repulsive force among them also increases.
- Neutrons, being neutral, do not contribute to this repulsive force. They help to stabilize the nucleus by providing an attractive force through the strong nuclear force without adding to the repulsion. Therefore, having more neutrons helps to offset the repulsive forces between the protons, making the nucleus more stable.

### Conclusion
Both statements are true, and Statement II correctly explains Statement I.

### Final Answer:
- **Statement I is true.**
- **Statement II is true and provides a correct explanation for Statement I.**

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