Question

Paramagnetism is shown by the molecules which have (a) paired electrons (b) unpaired electrons (c) lone paif of electrons (d) bond order more than one.

Short answer

Paramagnetism is exhibited by molecules with unpaired electrons, hence the answer is (b) unpaired electrons.

Step-by-step solution

Understanding Paramagnetism

Paramagnetism is a form of magnetism which occurs only in the presence of an external magnetic field. Paramagnetic materials have permanent magnetic moments, even in the absence of a magnetic field, due to the presence of unpaired electrons. An external magnetic field causes the unpaired electrons' spins to align parallel to the field, causing a net attraction.

Identifying Unpaired Electrons

According to the definition of paramagnetism, for a molecule to show paramagnetic behavior, it must have unpaired electrons. Hence, when examining the options given, we should look for the one that directly relates to the presence of unpaired electrons.

Evaluating the Options

Option (a) paired electrons: Molecules with all electrons paired will not show paramagnetism because they have no magnetic moments to align with a magnetic field. Option (c) lone pair of electrons: A lone pair of electrons, if paired, doesn't contribute to paramagnetism. Option (d) bond order more than one: While molecules with a higher bond order may have unpaired electrons, the bond order itself is not an indicator of unpaired electrons or paramagnetism. Therefore, the correct answer is based on the presence of unpaired electrons.

Key concepts

Unpaired Electrons

To explore the phenomenon of paramagnetism, one must first understand the role of unpaired electrons. Atoms and molecules possess electrons that revolve around the nucleus in defined energy levels or orbitals. These electrons tend to pair up within these orbitals, each with an opposite spin to the other.

However, not all electrons in an atom or molecule manage to find a perfect match; some remain solitary. These lone rangers are what we call unpaired electrons. It's the presence of these unpaired electrons that is crucial for paramagnetism. In a magnetic field, these electrons are like tiny magnets themselves, with their own magnetic properties due to their spin and orbital movement.

Understanding this, the correct answer to the exercise is (b) unpaired electrons. In an educational note, it's beneficial to present examples of paramagnetic materials, such as oxygen, to illustrate real-world substances where unpaired electrons play a pivotal role. Ensure students can identify unpaired electrons by using electron configuration and molecular orbital theory concepts.

Magnetic Moments

The concept of magnetic moments is closely linked to unpaired electrons and paramagnetism. A magnetic moment is essentially a vector quantity that represents the magnetic strength and orientation of a magnet or other object that produces a magnetic field. In the context of atoms and molecules, it's predominantly the unpaired electrons that contribute to the magnetic moment.

Each unpaired electron has a magnetic dipole moment associated with its spin. When you have multiple unpaired electrons, their individual moments can align and add up to produce a substantial magnetic effect. The elegance of this microscopic magnetic behavior is that it's not permanent; it depends on the influence of an external magnetic field. Without this external field, the unpaired electrons are randomly oriented due to thermal agitation, canceling out each other's magnetic effects.

For educational content, it is beneficial to use diagrams and magnetic vector illustrations to demonstrate how these individual magnetic moments of electrons influence the magnetic properties of the entire material.

External Magnetic Field

An external magnetic field is the final piece in the puzzle of understanding paramagnetism. Once a substance with unpaired electrons is placed in an external magnetic field, a fascinating transformation occurs. The unpaired electrons, which were randomly oriented, tend to align their spins with the direction of the field.

This alignment creates a situation where the magnetic moments of the electrons add constructively, resulting in a net magnetic field in the direction of the external field. Thus, the material experiences a force of attraction toward the source of the external magnetic field, displaying what we call paramagnetic behavior.

In the realm of education, it is vital to demonstrate this concept through experiments or simulations. For instance, showing a paramagnetic liquid in the presence of a strong magnet can provide a dramatic visualization of the magnetic alignment taking place. It's these practical connections between theory and real-world phenomena that solidify understanding for students.