🧲 Magnetic Properties of Solids | Class 12 Chemistry Notes
🌟 Introduction
Every electron in an atom has a magnetic moment due to its spin and orbital motion around the nucleus. When these magnetic moments align in a certain way, the material shows magnetism. Based on magnetic behavior, solids are classified into different types.
⚛️ Types of Magnetic Materials
Solids can be classified into five main types of magnetic materials:
- Diamagnetic Substances
- Paramagnetic Substances
- Ferromagnetic Substances
- Antiferromagnetic Substances
- Ferrimagnetic Substances
1️⃣ Diamagnetic Substances
Diamagnetic substances are weakly repelled by a magnetic field. They have no unpaired electrons, so their net magnetic moment is zero.
- Cause: Paired electrons cancel each other’s magnetic moment.
- Behavior: Weakly repelled by magnetic fields.
- Examples: Copper (Cu), Bismuth (Bi), Zinc (Zn), Water, Quartz.
2️⃣ Paramagnetic Substances
Paramagnetic materials are weakly attracted by a magnetic field and lose magnetism when the field is removed. They have unpaired electrons that align with the magnetic field.
- Cause: Presence of one or more unpaired electrons.
- Behavior: Weakly attracted by external magnetic fields.
- Examples: O₂, Ti³⁺, Fe³⁺, Cu²⁺, Cr³⁺.
3️⃣ Ferromagnetic Substances
Ferromagnetic materials are strongly attracted by magnetic fields and can retain magnetism permanently. Their magnetic moments are aligned in the same direction.
- Cause: Parallel alignment of magnetic moments.
- Behavior: Strongly attracted and remain magnetized.
- Examples: Iron (Fe), Nickel (Ni), Cobalt (Co).
- Uses: Used to make permanent magnets and electromagnets.
4️⃣ Antiferromagnetic Substances
In antiferromagnetic materials, the magnetic moments of neighboring atoms are aligned oppositely and cancel each other out.
- Cause: Equal and opposite alignment of magnetic dipoles.
- Behavior: Net magnetic moment is zero.
- Examples: Manganese oxide (MnO), Nickel oxide (NiO).
5️⃣ Ferrimagnetic Substances
In ferrimagnetic materials, the magnetic moments are aligned in opposite directions, but they are unequal, resulting in a net magnetic moment.
- Cause: Unequal opposing magnetic dipoles.
- Behavior: Weak magnetism compared to ferromagnets.
- Examples: Ferrites such as Fe₃O₄ (magnetite), ZnFe₂O₄.
📊 Summary Table of Magnetic Materials
| Type | Unpaired Electrons | Magnetic Behavior | Examples |
|---|---|---|---|
| Diamagnetic | None | Weakly repelled | Cu, Bi, Zn |
| Paramagnetic | One or more | Weakly attracted | O₂, Fe³⁺ |
| Ferromagnetic | Several | Strongly attracted, permanent magnet | Fe, Co, Ni |
| Antiferromagnetic | Several | Opposite alignment, no net magnetism | MnO, NiO |
| Ferrimagnetic | Several | Unequal opposite alignment, weak magnetism | Fe₃O₄, ZnFe₂O₄ |
🧠 Important Concepts
- Magnetic Moment (μ): Strength of magnetism associated with a particle or atom.
- Curie Temperature: The temperature above which ferromagnetic materials lose their magnetism.
- Domain Theory: Explains that ferromagnetic substances contain small magnetic regions (domains) that align when magnetized.
💡 Applications of Magnetic Materials
- Ferromagnetic materials are used to make electromagnets and transformers.
- Ferrimagnetic materials are used in magnetic storage devices and microwave devices.
- Paramagnetic materials are used in MRI machines and certain catalysts.
✨ Conclusion
The magnetic properties of solids depend on the arrangement of electrons and their magnetic moments. Understanding these properties helps in developing technologies such as motors, sensors, memory storage devices, and magnetic resonance machines.
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