Which substance shows anti ferro magnetism?

Options

A. `ZrO_(2)`
B. `CdO`
C. `CrO_(2)`
D. `V_(2)O_(3)`

Answer

To determine which substance shows antiferromagnetism, we need to understand the concept of antiferromagnetism and identify a suitable example.

### Step-by-Step Solution:

1. **Understanding Antiferromagnetism**:
- Antiferromagnetism is a type of magnetism that occurs in certain materials where adjacent ions or atoms have opposite magnetic moments. This means that in the presence of a magnetic field, the unpaired electrons in these materials will align in such a way that their magnetic moments cancel each other out.

2. **Characteristics of Antiferromagnetic Materials**:
- In antiferromagnetic materials, there are equal numbers of unpaired electrons that have opposite spins. This leads to a net magnetic moment of zero when the material is in a magnetic field.
- The spins of the electrons in these materials align in opposite directions, which is crucial for the antiferromagnetic behavior.

3. **Identifying Examples**:
- Common examples of antiferromagnetic materials include transition metal oxides. One well-known example is chromium oxide, which is represented as CrO2.

4. **Conclusion**:
- Based on the understanding of antiferromagnetism and the examples provided, the substance that shows antiferromagnetism is **chromium oxide (CrO2)**.

### Final Answer:
The substance that shows antiferromagnetism is **CrO2** (chromium oxide).