On decreasing intermolecular distance below the optimum distance (where potential energy is minimum), there is steep increase in potential energy due to:

Options

A. Increase in force of attraction between electrons and nucleus
B. Increase in stability of bonded atoms
C. Equal probability of finding bonding electrons near to either of nuclei
D. Increase in interelectronic and internuclear repulsion

Answer

To solve the question regarding the steep increase in potential energy when intermolecular distance is decreased below the optimum distance, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Intermolecular Forces**:
- Intermolecular forces are the forces that act between molecules. They can be classified into attractive and repulsive forces.
- Attractive forces include the attraction between electrons and nuclei, while repulsive forces arise from the interactions between like charges (nucleus-nucleus and electron-electron).

2. **Identifying Optimum Distance**:
- The optimum distance (or equilibrium distance) is the distance at which the potential energy of the system is at a minimum. At this point, the attractive and repulsive forces are balanced.
- Below this distance, the repulsive forces begin to dominate.

3. **Analyzing Potential Energy Curve**:
- The potential energy versus intermolecular distance curve typically shows a minimum point where the potential energy is lowest.
- As the intermolecular distance decreases below this minimum point, the potential energy sharply increases.

4. **Effects of Decreasing Distance**:
- When the intermolecular distance is decreased, the repulsive forces (inter-nuclear and inter-electronic) become significant.
- The repulsive forces arise from:
- **Nucleus-Nucleus Repulsion**: When nuclei come too close, they repel each other due to like charges.
- **Electron-Electron Repulsion**: Similarly, electrons repel each other when they are too close.

5. **Conclusion**:
- The steep increase in potential energy when the intermolecular distance is decreased below the optimum distance is primarily due to the increase in repulsive forces (both inter-nuclear and inter-electronic).
- Therefore, the correct answer is that the steep increase in potential energy is due to the increase in inter-electronic and inter-nuclear repulsion.

### Final Answer:
On decreasing intermolecular distance below the optimum distance, there is a steep increase in potential energy due to an increase in inter-electronic and inter-nuclear repulsion.

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