Which one is not diamagnetic substance?

Options

A. Cu
B. Sb
C. Bi
D. Cr

Explanation

To determine which substance is not diamagnetic, we need to understand the concept of diamagnetism and paramagnetism.

### Step-by-Step Solution:

1. **Understanding Diamagnetism**:
- Diamagnetic substances are those that do not have any unpaired electrons in their atomic or molecular structure. They are characterized by a weak repulsion from a magnetic field.

2. **Identifying Paramagnetism**:
- Paramagnetic substances, on the other hand, have one or more unpaired electrons. These unpaired electrons cause the substance to be attracted to a magnetic field.

3. **Analyzing the Options**:
- We need to examine the electronic configurations of the given options to identify which one has unpaired electrons.

4. **Electronic Configuration of Chromium**:
- The atomic number of chromium (Cr) is 24. Its electronic configuration is [Ar] 3d^5 4s^1.
- In this configuration, there is one unpaired electron in the 4s orbital and five unpaired electrons in the 3d orbitals.

5. **Conclusion**:
- Since chromium has unpaired electrons, it is not a diamagnetic substance. Instead, it exhibits paramagnetism due to these unpaired electrons.

6. **Final Answer**:
- Therefore, the substance that is not diamagnetic is **chromium**.