Number of diatomic molecules among the following is hydrogen molecule, ozone, water, carbon dioxide, sulphur dioxide, carbon monoxide, hydrogen chloride, oxygen molecule, sodium chloride.

Explanation

To determine the number of diatomic molecules from the given list, we will analyze each molecule based on the number of atoms it contains. A diatomic molecule is defined as one that consists of exactly two atoms.

**Step-by-Step Solution:**

1. **Identify the Molecules:**
The molecules we need to analyze are:
- Hydrogen molecule (H₂)
- Ozone (O₃)
...