Which is ferromagnetic?

Options

A. Co
B. Mg
C. Ag
D. Cu

Answer

To determine which of the given materials is ferromagnetic, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Magnetic Classification**:
- Materials can be classified based on their magnetic properties into three categories: diamagnetic, paramagnetic, and ferromagnetic.

2. **Identify Diamagnetic Materials**:
- Diamagnetic materials have all their electrons paired, resulting in no net magnetic moment. They are repelled by external magnetic fields. Examples include copper, silver, and gold.

3. **Identify Paramagnetic Materials**:
- Paramagnetic materials have some unpaired electrons, which allow them to align with an external magnetic field, but they do not retain magnetization once the field is removed. Magnesium is an example of a paramagnetic material.

4. **Identify Ferromagnetic Materials**:
- Ferromagnetic materials have a large number of unpaired electrons, leading to a net magnetic moment. They are strongly attracted to magnetic fields and can retain their magnetic properties even after the external field is removed. Examples include iron, nickel, and cobalt.

5. **Analyze the Given Options**:
- The options provided are:
- Cobalt
- Magnesium
- Silver
- Copper
- From our classification:
- Cobalt is ferromagnetic.
- Magnesium is paramagnetic.
- Silver and Copper are diamagnetic.

6. **Conclusion**:
- The only ferromagnetic material among the options is **Cobalt**.

### Final Answer:
Cobalt is the ferromagnetic material.

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