Which of the following is not an example of molecular crystal?

Options

A. Hydrogen
B. Iodine
C. Ice
D. Sodium chloride

Answer

To determine which of the following options is not an example of a molecular crystal, we need to analyze each option based on the type of bonding present in the substance.

### Step-by-Step Solution:

1. **Understanding Molecular Crystals**:
- Molecular crystals are solids where the constituent particles are molecules held together by weak intermolecular forces such as Van der Waals forces, hydrogen bonds, or dipole-dipole interactions.

2. **Analyzing Each Option**:
- **A. Hydrogen (H2)**:
- Hydrogen exists as diatomic molecules (H2). The intermolecular forces are weak dispersion forces. Therefore, hydrogen can be classified as a molecular crystal.

- **B. Iodine (I2)**:
- Iodine also exists as diatomic molecules (I2). The forces holding the molecules together are Van der Waals dispersion forces. Thus, iodine is a molecular crystal.

- **C. Ice (H2O)**:
- Ice is a solid form of water where the molecules are held together by hydrogen bonds. Although hydrogen bonds are stronger than Van der Waals forces, they are still considered weak compared to ionic or covalent bonds. Therefore, ice is classified as a molecular crystal.

- **D. Sodium Chloride (NaCl)**:
- Sodium chloride is composed of Na+ and Cl- ions held together by strong ionic bonds. Since it does not consist of molecules, but rather ions, sodium chloride is classified as an ionic crystal, not a molecular crystal.

3. **Conclusion**:
- The option that is not an example of a molecular crystal is **D. Sodium Chloride**.

### Final Answer:
**D. Sodium Chloride**