List two main conditions for forming hydrogen bonds.

Explanation

To form hydrogen bonds, two main conditions must be satisfied:

1. **High Electronegativity of the Atom Bonded to Hydrogen**: The atom that is bonded to hydrogen must have a high electronegativity. This means that elements such as fluorine (F), oxygen (O), and nitrogen (N) are typically involved in hydrogen bonding. These elements have a strong tendency to attract electrons, which leads to the formation of polar bonds.

2. **Small Size of the Electronegative Atom**: The electronegative atom should have a small atomic size. A smaller size allows for a stronger attraction between the bonded electron pair and the nucleus of the electronegative atom. This increased attraction enhances the polarity of the bond, which is crucial for the formation of hydrogen bonds.

### Summary of Conditions:
- **Condition 1**: The atom bonded to hydrogen must be highly electronegative (e.g., F, O, N).
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