Which of the following substance is diamagnetic ?

Options

A. `Fe_(3)O_(4)`
B. `MgFe_(2)O_(4)`
C. `ZnFe_(2)O_(4)`
D. NaCl

Answer

To determine which of the given substances is diamagnetic, we need to understand the concept of diamagnetism and identify the magnetic properties of the substances listed.

### Step-by-Step Solution:

1. **Understand Diamagnetism**:
- Diamagnetic substances are those that are not attracted to a magnetic field and are slightly repelled by it. They have all their electrons paired, which means there are no unpaired electrons.

2. **Identify the Substances**:
- The substances mentioned in the question are:
- Fe3O4 (Iron(II,III) oxide)
- MgFe2O4 (Magnesium ferrite)
- ZnFe2O4 (Zinc ferrite)
- NaCl (Sodium chloride)

3. **Analyze Each Substance**:
- **Fe3O4**: This is a ferrimagnetic material, meaning it has unpaired electrons and is attracted to a magnetic field.
- **MgFe2O4**: This is also a ferrimagnetic material, containing unpaired electrons, thus it is not diamagnetic.
- **ZnFe2O4**: This is a superparamagnetic material, which also has unpaired electrons and is not diamagnetic.
- **NaCl**: Sodium chloride is an ionic compound where all electrons are paired, making it a diamagnetic substance.

4. **Conclusion**:
- Among the substances listed, NaCl is the only diamagnetic substance.

### Final Answer:
- The diamagnetic substance is **NaCl**.