Question

The paramagnetism is due to the presence of (a) paired electrons (b) unpaired electrons (c) both paired as well as unpaired electrons (d) none of these

Short answer

The correct answer is: (b) unpaired electrons

Step-by-step solution

Understanding the Concepts

Start by understanding what paramagnetism is, i.e. a type of induced magnetism, associated with unpaired electrons. Substances with unpaired electrons are attracted by magnetic fields, which classifies them as paramagnetic.

Analyzing the Options

Each option should then be analyzed based on this understanding. Option (a) and option (c) suggest paired electrons, which would not cause paramagnetism. Option (d) negates all the choices, which would mean paramagnetism isn't caused by electrons, which we know is untrue.

Selection of the Correct Option

Based on the analysis, option (b) that states paramagnetism is due to unpaired electrons is identified to be the correct answer.

Key concepts

Unpaired Electrons and Paramagnetism

Understanding the role of unpaired electrons in paramagnetism is fundamental to grasping why certain materials are attracted to magnetic fields. These electrons have a property called 'spin', and when an electron is unpaired, its spin is not canceled out by another electron with an opposite spin.

Materials that exhibit paramagnetism contain atoms or ions with at least one unpaired electron. Such electrons generate their own magnetic field, which aligns with the external magnetic field when the material is exposed to it. This alignment is what causes attraction. For example, elements like oxygen and aluminum have unpaired electrons, making them paramagnetic. Conversely, elements like nitrogen, which have all electrons paired, do not exhibit paramagnetism.

Key Takeaway

It's the unpaired electrons in the atomic or molecular structure that are responsible for the magnetic properties known as paramagnetism. Hence, in our textbook exercise, option (b) 'unpaired electrons' correctly explains the cause of paramagnetism.

Induced Magnetism

Induced magnetism occurs when a material temporarily becomes magnetized in the presence of an external magnetic field. The strength of this induced magnetism is proportional to the strength of the external magnetic field and largely depends on the nature of the material.

For paramagnetic materials, the magnetization is induced by the alignment of unpaired electron spins when an external magnetic field is applied. This is a weak form of magnetism and typically vanishes when the magnetic field is removed, demonstrating that paramagnetic materials do not retain significant magnetization on their own.

Real-life Example

Using a strong magnet near a paper clip (which is normally not magnetic) can induce temporary magnetization. However, once the external magnetic field is removed, the paper clip will lose its magnetism. This illustrates the temporary and dependent nature of induced magnetism in paramagnetic materials.

Magnetic Fields

Magnetic fields are invisible fields that exert a force on substances that are either magnetic or can be magnetized. They are vector fields, with both a direction and magnitude, and are represented by the symbol \( B \) commonly referred to as the magnetic flux density or magnetic induction.

Magnetic fields are generated by moving electric charges, such as the flow of electrons in a wire, and by the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. The way in which the magnetic field lines emerge and return to a magnet influences how other materials interact with the field.

Visualization of Magnetic Fields

One way to visualize a magnetic field is through the use of iron filings sprinkled on a piece of paper above a magnet. The filings align themselves along the field lines, forming patterns that reveal the direction and contours of the magnetic field.