Number of `H_(2)` molecules attached to each `H_(2)O` molecule through hydrogen bonding is

Explanation

To determine the number of \( H_2 \) molecules attached to each \( H_2O \) molecule through hydrogen bonding, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Hydrogen Bonding**:
- Hydrogen bonding occurs when a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen in water) interacts with another electronegative atom. In the case of water, the hydrogen atoms of one \( H_2O \) molecule can form hydrogen bonds with the oxygen atom of another \( H_2O \) molecule.

2. **Structure of Water**:
- Each \( H_2O \) molecule has a bent shape with an angle of about 104.5 degrees between the hydrogen atoms. The oxygen atom has two lone pairs of electrons.

3. **Hydrogen Bonding in Water**:
- Each \( H_2O \) molecule can form hydrogen bonds using its two hydrogen atoms and its two lone pairs of electrons.
- The oxygen atom of one water molecule can form hydrogen bonds with the hydrogen atoms of two neighboring water molecules.

4. **Counting the Hydrogen Bonds**:
- Each \( H_2O \) molecule can form hydrogen bonds with a total of four other \( H_2O \) molecules:
- Two hydrogen bonds with the lone pairs of oxygen.
- Two hydrogen bonds with the hydrogen atoms of neighboring water molecules.

5. **Conclusion**:
- Therefore, each \( H_2O \) molecule can be attached to **four** \( H_2O \) molecules through hydrogen bonding.

### Final Answer:
The number of \( H_2O \) molecules attached to each \( H_2O \) molecule through hydrogen bonding is **4**.

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