Inaugurated by IN-SPACe
ISRO Registered Space Tutor
S7-SA5-0728
What is Paramagnetism (Molecular Orbital Theory)?
Grade Level:
Class 12
AI/ML, Physics, Biotechnology, FinTech, EVs, Space Technology, Climate Science, Blockchain, Medicine, Engineering, Law, Economics
Definition
What is it?
Paramagnetism is a property of substances that are weakly attracted to a magnetic field. This happens when a substance has one or more unpaired electrons in its molecular orbitals, as explained by Molecular Orbital Theory.
Simple Example
Quick Example
Imagine you have a small magnet, like the one on your fridge. If you bring it near a tiny piece of iron, it sticks. Now, imagine bringing it near a special type of salt, like copper sulfate. It won't stick strongly like iron, but you might feel a very slight pull. This slight pull shows paramagnetism, caused by unpaired electrons inside the copper sulfate.
Worked Example
Step-by-Step
Let's figure out if Oxygen (O2) is paramagnetic using Molecular Orbital Theory:
1. First, find the total number of electrons in O2. Each Oxygen atom has 8 electrons, so O2 has 8 + 8 = 16 electrons.
---2. Next, fill these 16 electrons into the molecular orbitals in order: sigma(1s), sigma*(1s), sigma(2s), sigma*(2s), sigma(2pz), pi(2px), pi(2py), pi*(2px), pi*(2py), sigma*(2pz).
---3. Remember to fill orbitals according to Hund's rule (one electron in each degenerate orbital before pairing) and Pauli exclusion principle (max two electrons per orbital with opposite spins).
---4. Filling 16 electrons: sigma(1s)^2, sigma*(1s)^2, sigma(2s)^2, sigma*(2s)^2, sigma(2pz)^2, pi(2px)^2, pi(2py)^2, pi*(2px)^1, pi*(2py)^1.
---5. Look at the highest occupied molecular orbitals (HOMOs). We see that the pi*(2px) and pi*(2py) orbitals each have one electron. These are unpaired electrons.
---6. Since O2 has two unpaired electrons, it is paramagnetic.
ANSWER: Oxygen (O2) is paramagnetic because it has two unpaired electrons in its pi* antibonding molecular orbitals.
Why It Matters
Understanding paramagnetism helps scientists design new materials for computers and magnetic storage devices. In medicine, it's used in MRI machines to see inside the body without surgery. Engineers use this knowledge to develop advanced sensors and catalysts, impacting fields like AI/ML and biotechnology.
Common Mistakes
MISTAKE: Assuming all molecules with an even number of electrons are diamagnetic. | CORRECTION: Always apply Molecular Orbital Theory to check for unpaired electrons, especially for diatomic molecules like O2, which has an even number of electrons but is paramagnetic.
MISTAKE: Confusing paramagnetism with ferromagnetism. | CORRECTION: Paramagnetism is a weak attraction to a magnetic field, while ferromagnetism is a very strong, permanent attraction (like a fridge magnet). Paramagnetism disappears when the external field is removed.
MISTAKE: Incorrectly filling molecular orbitals or forgetting Hund's rule. | CORRECTION: Always fill degenerate orbitals (like pi and pi* orbitals) with one electron each before pairing them up. Follow the correct energy order of molecular orbitals.
Practice Questions
Try It Yourself
QUESTION: Is Nitrogen (N2) paramagnetic or diamagnetic? (Atomic number of N = 7) | ANSWER: Diamagnetic
QUESTION: Using Molecular Orbital Theory, determine if C2 is paramagnetic or diamagnetic. (Atomic number of C = 6) | ANSWER: Diamagnetic
QUESTION: Explain why B2 is paramagnetic, even though it has an even number of electrons. (Atomic number of B = 5) | ANSWER: B2 has 10 electrons. Its MO configuration is sigma(1s)^2, sigma*(1s)^2, sigma(2s)^2, sigma*(2s)^2, pi(2px)^1, pi(2py)^1. It has two unpaired electrons in the degenerate pi(2px) and pi(2py) bonding orbitals, making it paramagnetic.
MCQ
Quick Quiz
Which of the following molecules is paramagnetic?
H2
N2
F2
O2
The Correct Answer Is:
D
O2 has two unpaired electrons in its antibonding pi* molecular orbitals, making it paramagnetic. H2, N2, and F2 all have all their electrons paired, making them diamagnetic.
Real World Connection
In the Real World
In India, paramagnetism principles are used in medical imaging like MRI (Magnetic Resonance Imaging) scans, which help doctors at hospitals like AIIMS see detailed images of organs and tissues inside the body. Also, researchers at institutions like IITs are exploring paramagnetic materials for advanced data storage in next-gen computers.
Key Vocabulary
Key Terms
PARAMAGNETISM: Weak attraction to a magnetic field due to unpaired electrons | MOLECULAR ORBITAL THEORY: A model explaining how atomic orbitals combine to form molecular orbitals | UNPAIRED ELECTRONS: Electrons occupying an orbital alone, not paired with another electron | DIAMAGNETISM: Weak repulsion from a magnetic field due to all electrons being paired | BONDING ORBITAL: A molecular orbital that is lower in energy than the atomic orbitals from which it was formed
What's Next
What to Learn Next
Great job understanding paramagnetism! Next, you can explore 'Diamagnetism and its applications' to understand how substances with all paired electrons behave in a magnetic field. This will give you a complete picture of magnetic properties of materials.
